Send a message

F3b — hold the message for HUMAN approval instead of delivering: accepted, signed and stored, not sent. The 202 answers status held with approve/reject URLs; the human decides in the portal, by Telegram, or by POST /v1/messages/{id}/approve|reject (scope approve:holds — the key that sends is not the key that approves). Default TTL 24 h, max 7 days; expired drafts never go out. Counts one quota unit per recipient at acceptance; rejected/expired refunds it. Ignored (status sandbox) when the key itself is in sandbox.

Seconds until the draft expires (default 86400).

What the agent wants the approver to know.

a@b.com or Name <a@b.com>; the domain must be verified in the account. Exactly one address: the display name cannot carry another address, and a bare address is the whole value (a@b.com (Name) and Name a@b.com are 400). At most 998 characters (the RFC 5322 line limit). The display name may have accents; the address is ASCII only (an IDN domain in xn-- form), with no Unicode space next to it — otherwise 400 with reason: address_not_ascii.

At least one of html/text is required — unless templateId is used.

Pins a published template version.

Optional task/order key (alternative to the Idempotency-Key header). Within the account, a retained key returns the original message id for 24 hours from its first claim. After expiry a retry can create another message.

true accepts and freezes without delivering (or header X-Oveyon-Sandbox: 1).

The envelope sender (Return-Path) of THIS message; without it, the key's default applies (set under Credentials). platform (the default for new keys): a per-message platform address — bounces come back to us, show up on the message, fire the bounce webhook and suppress addresses that do not exist. sender: the envelope is the From address itself, stable across messages — for a personal mailbox and mailing lists (list confirmation, greylisting, allowlists by envelope sender); a bounce the destination sends back goes straight to the sender's mailbox and is NOT tracked (no suppression, no bounce webhook) — an immediate refusal our server sees still shows up in the message status. sender requires the From domain to authorize us: its SPF must have our include: (and the _mailchannels TXT when that relay is active) — otherwise 422 return_path_not_authorized. sender is for paid plans: on an account without one it is 403 return_path_requires_paid_plan (unless our team switched the key to sender as an exception); a key whose default is sender on an account that moved to a free plan simply sends with the platform address. Any other value (an address included) is 400.

The id of the ORIGINAL message (the one the idempotencyKey created).