Send a mailbox message
Creates and queues a message from the authenticated mailbox. Supply an Idempotency-Key header to safely retry. Attachments may use small inline base64 content or blob IDs returned by POST /mailbox/attachments:upload or POST /mailbox/attachment-uploads.
Authorizations
Sendmux API key. Use a root API key for Management API routes, or a mailbox credential for Mailbox API routes. Obtain keys from the dashboard under API Keys.
Headers
Client-chosen unique key to safely retry the request. Cached for 24h per (mailbox, endpoint, key). Different body with same key returns 409 idempotency_conflict.
255Query Parameters
Mailbox public ID to target when the credential grants access to more than one mailbox. Omit when the credential is scoped to exactly one mailbox.
Body
Subject line for the outgoing email.
Primary recipients.
1Attachments to send with the message.
- Option 1
- Option 2
BCC recipients.
CC recipients.
Custom headers to include.
Sender address. Defaults to mailbox identity.
HTML body.
Reply-To recipients.
Plain text body.