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POST
Send Message
CLI:

Overview

Sends a message in an existing Unibox thread. For a new one-off email, first call Create thread, then call this endpoint with threading_mode: "new_thread". For an existing email or LinkedIn conversation, call this endpoint on the existing thread to reply from the connected sender.

Path Parameters

Request Body

Attachment uploads are available only to authenticated dashboard sessions. Public API and CLI callers must omit attachments.

Send a One-Off Email

On success, the response includes the saved outbound message and the refreshed thread. A one-off outbound email appears in Unibox with thread.inbox_state set to sent_one_off.

Error Notes

AI agent notes

For a brand-new one-off email, create the thread first and send with threading_mode: "new_thread". Do not retry a 500 response that says the message was sent but could not be saved, because the recipient may already have received it.

Authorizations

Authorization
string
header
required

Bearer authentication header of the form Bearer <token>, where <token> is your auth token.

Path Parameters

id
string
required

Thread (conversations.id) UUID.

Body

application/json
body_text
string
required

Plain-text message body.

Minimum string length: 1
body_html
string

Optional HTML message body.

subject
string

Email subject.

account_id
string

Email sender account ID.

cc
string

Email CC recipients.

bcc
string

Email BCC recipients.

threading_mode
enum<string>

Email threading behavior.

Available options:
new_thread,
reply
attachments
object[] | null

Uploaded attachment metadata.

Response

Successful response.