---
title: "Get Scheduled Email"
method: GET
path: "/emails/scheduled/{transmissionId}"
tags: ["Emails"]
---

# Get Scheduled Email

`GET /emails/scheduled/{transmissionId}`

## Request

- Base URL: `https://app.lettr.com/api`
- URL: `https://app.lettr.com/api/emails/scheduled/{transmissionId}`
- Auth: HTTP bearer

Retrieve a scheduled email by the `request_id` returned when it was scheduled (`sch_...`).

**Breaking change.** Scheduled emails are no longer parked inside SparkPost with `options.start_time`, because SparkPost retired its per-transmission GET endpoint. Lettr now answers from its own store, so the response is correct the instant the email is scheduled and a cancelled email can be told apart from one that never existed. `request_id` is Lettr's own `sch_...` id, SparkPost's id is the separate `transmission_id` field (`null` until the email is injected, and the value that appears as `transmission_id` on your webhook events), and `state` is one of `scheduled`, `sending`, `sent`, `cancelled` or `failed`.

For emails scheduled **before** this change there is no Lettr record, only the SparkPost transmission id you stored. Those ids are still accepted and fall back to a delivery-events lookup, which returns the **old** response shape (`ShowScheduledTransmissionResponse`, with SparkPost's pass-through `state` values and no `request_id`).

A sandbox key only sees the emails it scheduled itself.

## Path parameters

- `transmissionId` string, required

## Response `200`

Scheduled transmission retrieved successfully. Returns the scheduled email when Lettr knows the id, or the legacy events-derived shape for a SparkPost transmission id from before this change.

- union
  - object: Returned for a `sch_...` id that Lettr knows about.
    - `message` string, required
    - `data` ScheduledEmailResponse, required: A scheduled email held by Lettr. This is the `data` object of `POST /emails/scheduled`, `GET /emails/scheduled/{transmissionId}` and `DELETE /emails/scheduled/{transmissionId}`, and each entry of `scheduled_emails` in `GET /emails/scheduled`. **Breaking change.** Scheduled emails are no longer parked inside SparkPost with `options.start_time` — SparkPost retired its per-transmission GET and DELETE endpoints. Lettr now holds the email in its own store and injects it into SparkPost when it is due, so `request_id` is Lettr's own `sch_...` id, `transmission_id` is a separate field that stays `null` until injection, and `state` values are Lettr's own rather than SparkPost's pass-through states.
      - `request_id` string, required: Lettr's identifier for the scheduled email, prefixed `sch_`. Pass this value to `GET` and `DELETE /emails/scheduled/{transmissionId}`. Before this change the field held SparkPost's transmission id.
      - `transmission_id` string, nullable, required: SparkPost's transmission id. `null` until the email is injected into SparkPost at its delivery time. This is the value that appears as `transmission_id` on your webhook events, so correlate webhooks on this field — not on `request_id`.
      - `state` 'scheduled' | 'sending' | 'sent' | 'cancelled' | 'failed', required: Current state of the scheduled email. `scheduled` — waiting for its delivery time, the only state that can be cancelled. `sending` — claimed by the dispatcher and being injected right now. `sent` — injected into SparkPost; delivery detail then comes from `events`. `cancelled` — cancelled before injection, never handed to SparkPost. `failed` — injection was attempted and gave up, see `failure_reason`.
      - `scheduled_at` string, date-time, required: The delivery time in ISO 8601 format (UTC).
      - `from` string, email, required: Sender email address.
      - `from_name` string, nullable, required: Sender display name.
      - `subject` string, nullable, required: Email subject line.
      - `recipients` string[], required: List of recipient email addresses.
      - `num_recipients` integer, required: Total number of recipients.
      - `accepted` integer, required: Number of recipients accepted for delivery. Before injection this is what Lettr accepted; afterwards it is SparkPost's own count.
      - `rejected` integer, required: Number of recipients rejected. `0` before injection.
      - `tag` string, nullable, required: Tag supplied when the email was scheduled, used for tracking and analytics.
      - `failure_reason` string, nullable, required: Why injection gave up. Only set when `state` is `failed`.
      - `events` EmailEvent[], required: Delivery events for this email. Empty until the email has been sent; populated with injection, delivery, bounce, open, click and other events once it has been injected into SparkPost.
        - union: An email event. The `type` field determines which additional fields are present. All event types share common fields defined in `CommonEventProperties`.
          - InjectionEvent: Fired when a message is received by the system and queued for delivery.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'injection', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `initial_pixel` boolean, nullable: Whether initial open tracking pixel was included
          - DeliveryEvent: Fired when a message is successfully delivered to the recipient's mail server.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'delivery', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `queue_time` integer, nullable: Time spent in queue in milliseconds
            - `outbound_tls` string, nullable: Whether TLS was used for outbound delivery ("1" = yes)
          - BounceEvent: Fired when a message is permanently rejected by the recipient's mail server.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'bounce', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `bounce_class` integer, nullable: Bounce classification code (e.g. 10 = Invalid Recipient, 30 = Generic Bounce)
            - `error_code` string, nullable: SMTP error code
            - `reason` string, nullable: Human-readable bounce reason
            - `raw_reason` string, nullable: Raw SMTP reason string
            - `num_retries` integer, nullable: Number of delivery retries attempted
            - `device_token` string, nullable: Device token if applicable
          - DelayEvent: Fired when a message delivery is temporarily delayed (will be retried).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'delay', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `reason` string, nullable: Human-readable delay reason
            - `raw_reason` string, nullable: Raw SMTP reason string
            - `error_code` string, nullable: SMTP error code
            - `bounce_class` integer, nullable: Bounce classification code
            - `num_retries` integer, nullable: Number of delivery retries attempted so far
            - `queue_time` integer, nullable: Time spent in queue in milliseconds
            - `outbound_tls` string, nullable: Whether TLS was used for outbound delivery
          - OutOfBandEvent: Fired when a remote mail server sends an asynchronous bounce after initially accepting the message.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'out_of_band', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `bounce_class` integer, nullable: Bounce classification code
            - `error_code` string, nullable: SMTP error code
            - `reason` string, nullable: Human-readable bounce reason
            - `raw_reason` string, nullable: Raw SMTP reason string
            - `device_token` string, nullable: Device token if applicable
          - SpamComplaintEvent: Fired when a recipient marks the message as spam via a feedback loop.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'spam_complaint', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `fbtype` string, nullable: Feedback type (e.g. "abuse")
            - `report_by` string, nullable: Who reported the spam
            - `report_to` string, nullable: Where the spam report was sent
          - PolicyRejectionEvent: Fired when a message is rejected due to policy (e.g. suppression list, rate limiting).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'policy_rejection', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `remote_addr` string, nullable: Remote IP address
            - `reason` string, nullable: Human-readable rejection reason
            - `raw_reason` string, nullable: Raw rejection reason
            - `error_code` string, nullable: Error code
            - `bounce_class` integer, nullable: Bounce classification code
          - ClickEvent: Fired when a recipient clicks a tracked link in the email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'click', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `target_link_url` string, nullable: The URL that was clicked
            - `target_link_name` string, nullable: The name/label of the clicked link
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the click
          - OpenEvent: Fired when a recipient opens the email (subsequent opens after the initial open).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - InitialOpenEvent: Fired the first time a recipient opens the email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'initial_open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - AmpClickEvent: Fired when a recipient clicks a tracked link in an AMP email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'amp_click', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `target_link_url` string, nullable: The URL that was clicked
            - `target_link_name` string, nullable: The name/label of the clicked link
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the click
          - AmpOpenEvent: Fired when a recipient opens an AMP email (subsequent opens).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'amp_open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - AmpInitialOpenEvent: Fired the first time a recipient opens an AMP email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'amp_initial_open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - GenerationFailureEvent: Fired when the system fails to generate a message (e.g. template rendering error).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'generation_failure', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `reason` string, nullable: Human-readable failure reason
            - `raw_reason` string, nullable: Raw failure reason
            - `error_code` string, nullable: Error code
          - GenerationRejectionEvent: Fired when the system rejects message generation (e.g. policy violation).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'generation_rejection', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `reason` string, nullable: Human-readable rejection reason
            - `raw_reason` string, nullable: Raw rejection reason
            - `error_code` string, nullable: Error code
          - ListUnsubscribeEvent: Fired when a recipient uses the List-Unsubscribe header to unsubscribe.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'list_unsubscribe', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
          - LinkUnsubscribeEvent: Fired when a recipient clicks an unsubscribe link in the email body.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'link_unsubscribe', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
  - ShowScheduledTransmissionResponse
    - `message` string, required
    - `data` object, required
      - `transmission_id` string, required: The unique transmission ID.
      - `state` 'submitted' | 'generating' | 'scheduled' | 'delivered' | 'bounced' | 'failed' | 'unknown', required: Current state of the transmission. `submitted`/`generating` — still pending in SparkPost. `scheduled` — injected but not yet delivered (has `injection` event only). `delivered` — successfully delivered. `bounced` — rejected by recipient server. `failed` — generation or policy failure.
      - `scheduled_at` string, date-time, nullable: The scheduled delivery time in ISO 8601 format. Present when the transmission is still pending. May be `null` when the transmission has already been delivered.
      - `from` string, email, required: Sender email address.
      - `from_name` string, nullable: Sender display name.
      - `subject` string, required: Email subject line.
      - `recipients` string[], required: List of recipient email addresses.
      - `num_recipients` integer, required: Total number of recipients.
      - `events` EmailEvent[], required: Delivery events for this transmission. Empty array when the email is still scheduled. Populated with delivery, bounce, open, click, and other events once the email has been processed.
        - union: An email event. The `type` field determines which additional fields are present. All event types share common fields defined in `CommonEventProperties`.
          - InjectionEvent: Fired when a message is received by the system and queued for delivery.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'injection', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `initial_pixel` boolean, nullable: Whether initial open tracking pixel was included
          - DeliveryEvent: Fired when a message is successfully delivered to the recipient's mail server.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'delivery', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `queue_time` integer, nullable: Time spent in queue in milliseconds
            - `outbound_tls` string, nullable: Whether TLS was used for outbound delivery ("1" = yes)
          - BounceEvent: Fired when a message is permanently rejected by the recipient's mail server.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'bounce', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `bounce_class` integer, nullable: Bounce classification code (e.g. 10 = Invalid Recipient, 30 = Generic Bounce)
            - `error_code` string, nullable: SMTP error code
            - `reason` string, nullable: Human-readable bounce reason
            - `raw_reason` string, nullable: Raw SMTP reason string
            - `num_retries` integer, nullable: Number of delivery retries attempted
            - `device_token` string, nullable: Device token if applicable
          - DelayEvent: Fired when a message delivery is temporarily delayed (will be retried).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'delay', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `reason` string, nullable: Human-readable delay reason
            - `raw_reason` string, nullable: Raw SMTP reason string
            - `error_code` string, nullable: SMTP error code
            - `bounce_class` integer, nullable: Bounce classification code
            - `num_retries` integer, nullable: Number of delivery retries attempted so far
            - `queue_time` integer, nullable: Time spent in queue in milliseconds
            - `outbound_tls` string, nullable: Whether TLS was used for outbound delivery
          - OutOfBandEvent: Fired when a remote mail server sends an asynchronous bounce after initially accepting the message.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'out_of_band', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `bounce_class` integer, nullable: Bounce classification code
            - `error_code` string, nullable: SMTP error code
            - `reason` string, nullable: Human-readable bounce reason
            - `raw_reason` string, nullable: Raw SMTP reason string
            - `device_token` string, nullable: Device token if applicable
          - SpamComplaintEvent: Fired when a recipient marks the message as spam via a feedback loop.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'spam_complaint', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `fbtype` string, nullable: Feedback type (e.g. "abuse")
            - `report_by` string, nullable: Who reported the spam
            - `report_to` string, nullable: Where the spam report was sent
          - PolicyRejectionEvent: Fired when a message is rejected due to policy (e.g. suppression list, rate limiting).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'policy_rejection', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `remote_addr` string, nullable: Remote IP address
            - `reason` string, nullable: Human-readable rejection reason
            - `raw_reason` string, nullable: Raw rejection reason
            - `error_code` string, nullable: Error code
            - `bounce_class` integer, nullable: Bounce classification code
          - ClickEvent: Fired when a recipient clicks a tracked link in the email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'click', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `target_link_url` string, nullable: The URL that was clicked
            - `target_link_name` string, nullable: The name/label of the clicked link
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the click
          - OpenEvent: Fired when a recipient opens the email (subsequent opens after the initial open).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - InitialOpenEvent: Fired the first time a recipient opens the email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'initial_open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - AmpClickEvent: Fired when a recipient clicks a tracked link in an AMP email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'amp_click', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `target_link_url` string, nullable: The URL that was clicked
            - `target_link_name` string, nullable: The name/label of the clicked link
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the click
          - AmpOpenEvent: Fired when a recipient opens an AMP email (subsequent opens).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'amp_open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - AmpInitialOpenEvent: Fired the first time a recipient opens an AMP email.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'amp_initial_open', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `user_agent` string, nullable: Raw user agent string
            - `user_agent_parsed` UserAgentParsed: Parsed user agent information from the open/click event.
              - …
            - `geo_ip` GeoIp: Geolocation data derived from the IP address of the open/click event.
              - …
            - `ip_address` string, nullable: IP address of the open
            - `initial_pixel` boolean, nullable: Whether this was triggered by the initial tracking pixel
          - GenerationFailureEvent: Fired when the system fails to generate a message (e.g. template rendering error).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'generation_failure', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `reason` string, nullable: Human-readable failure reason
            - `raw_reason` string, nullable: Raw failure reason
            - `error_code` string, nullable: Error code
          - GenerationRejectionEvent: Fired when the system rejects message generation (e.g. policy violation).
            - `event_id` string, required: Unique identifier for the event
            - `type` 'generation_rejection', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
            - `reason` string, nullable: Human-readable rejection reason
            - `raw_reason` string, nullable: Raw rejection reason
            - `error_code` string, nullable: Error code
          - ListUnsubscribeEvent: Fired when a recipient uses the List-Unsubscribe header to unsubscribe.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'list_unsubscribe', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version
          - LinkUnsubscribeEvent: Fired when a recipient clicks an unsubscribe link in the email body.
            - `event_id` string, required: Unique identifier for the event
            - `type` 'link_unsubscribe', required: The event type
            - `timestamp` string, required: When the event occurred (ISO 8601)
            - `request_id` string, required: The transmission/request ID that generated this event
            - `rcpt_to` string, email, required: Recipient email address
            - `raw_rcpt_to` string, email, required: Original recipient email address before any modifications
            - `recipient_domain` string, required: Domain of the recipient
            - `mailbox_provider` string, required: Mailbox provider of the recipient
            - `mailbox_provider_region` string, required: Region of the mailbox provider
            - `message_id` string, nullable: SMTP message ID
            - `subject` string, nullable: Email subject line
            - `friendly_from` string, nullable: Friendly from address
            - `sending_domain` string, nullable: The sending domain
            - `sending_ip` string, nullable: IP address used to send the email
            - `click_tracking` boolean, nullable: Whether click tracking was enabled
            - `open_tracking` boolean, nullable: Whether open tracking was enabled
            - `transactional` boolean, nullable: Whether this was a transactional message
            - `msg_size` integer, nullable: Message size in bytes
            - `injection_time` string, nullable: When the message was injected into the system (ISO 8601)
            - `rcpt_meta` unknown
            - `campaign_id` string, nullable: Campaign identifier
            - `template_id` string, nullable: Template identifier
            - `template_version` string, nullable: Template version
            - `ip_pool` string, nullable: IP pool used for sending
            - `msg_from` string, nullable: Envelope sender (MAIL FROM)
            - `rcpt_type` string, nullable: Recipient type
            - `rcpt_tags` string[], nullable: Recipient tags
            - `amp_enabled` boolean, nullable: Whether AMP was enabled
            - `delv_method` string, nullable: Delivery method (e.g. esmtp)
            - `recv_method` string, nullable: Reception method (e.g. rest)
            - `routing_domain` string, nullable: Routing domain
            - `scheduled_time` string, nullable: Scheduled delivery time if the email was scheduled
            - `ab_test_id` string, nullable: A/B test identifier
            - `ab_test_version` string, nullable: A/B test version

## Other responses

- `401`: Unauthorized - Missing or invalid API key
- `403`: Forbidden - API key does not have the required scope
- `404`: Scheduled transmission not found
- `500`: Internal server error
- `503`: Service unavailable - the API key could not be verified, so the request was not processed. This does not mean the key is invalid; retry after the delay given in the Retry-After header.

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[API](https://skmtc.dev/lettr/apis/lettr-api.md) · [All operations](https://skmtc.dev/lettr/apis/lettr-api/llms.txt) · [OpenAPI document](https://skmtc.dev/lettr/apis/lettr-api/revisions/48ef0dac1ebd?raw)