---
title: "Who an email to a signer comes from when no mailbox is named"
method: GET
path: "/api/v1/firme/mail-sender"
tags: ["Signatures (app routes)"]
---

# Who an email to a signer comes from when no mailbox is named

`GET /api/v1/firme/mail-sender`

## Request

- Base URL: `https://api.custodo.ai`
- URL: `https://api.custodo.ai/api/v1/firme/mail-sender`
- Auth: HTTP bearer

An envelope without `mailAccountId` writes from the organisation’s own mailbox when `invitationSender` is `tenant` and one can send, otherwise from Custodo’s relay: `relay.address`, under the organisation’s name. A named mailbox that stopped being active falls back the same way.

## Headers

- `X-Tenant-Id` string, uuid

## Response `200`

The default sender.

- object
  - `ok` true, required
  - `data` FirmeMailSender, required
    - `relay` object, required
      - `name` string, required: The organisation’s name, which the relay’s messages carry.
      - `address` string, nullable, required: Custodo’s sending address; null without a relay.
    - `invitationSender` 'platform' | 'tenant', required

## Other responses

- `400`: The request did not validate: `error.details` names the fields.
- `401`: No API key, or one that is malformed, unknown, revoked or expired.
- `403`: The module is off for this organisation, the credential lacks the permission, or the tier does not cover it.
- `429`: The API key has spent its minute, or its day. See `Retry-After`.

---

[API](https://skmtc.dev/custodo/apis/custodo-integrazioni.md) · [All operations](https://skmtc.dev/custodo/apis/custodo-integrazioni/llms.txt) · [OpenAPI document](https://skmtc.dev/custodo/apis/custodo-integrazioni/revisions/16d336d3ec2a?raw)