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POST
Schedule send

Authorizations

x-api-key
string
header
required

API key (sk-proj-…) from Settings → API Keys. Required for sold API calls outside the Mermail console.

Path Parameters

mailboxId
string
required

Mailbox public_id (UUID), hosted alias id, or current email

Body

application/json
body
string
required
Example:

"<p>See you</p>"

scheduled_send_at
string<date-time>
required

Must be in the future (ISO-8601)

Example:

"2026-07-16T15:00:00.000Z"

to
Example:
cc
bcc
subject
string
Example:

"Later"

in_reply_to
string
thread_id
string
draft_id
string
attachments
object[]

Base64 file bytes or an existing attachment_id from the same authorized mailbox. Omit to preserve attachments from source_draft_id (send) or draft_id (save/schedule); [] clears; an array replaces the complete set. Storage limits: 20 files, 10 MiB each, 25 MiB decoded total. Encoded message limits include overhead: about 5 MiB for hosted addresses and about 40 MB for custom-domain addresses. Local paths and URLs are not accepted.

Maximum array length: 20

Response

Success

The response is of type object.