Message Submission

WildDuck allows sending emails directly through the HTTP API, without requiring an SMTP client. This is particularly useful for webmail interfaces and automated systems.

Endpoint

POST /users/:user/submit

This endpoint composes a message and, by default, queues it for delivery through the configured sender queue. It normally stores a copy in Sent Mail. Set isDraft to store a draft without delivery, or uploadOnly to store without queueing.

Request Format

The request body includes:

• from — Optional sender address, resolved against the user's addresses and sender policy
• to / cc / bcc — Recipient addresses
• subject — Message subject
• text — Plain text body
• html — HTML body
• headers — Custom headers (optional)
• attachments — File attachments (optional)
• reference — Reference to previous message for replies/forwards (object with mailbox, id, and action fields where action is reply, replyAll, or forward)
• isDraft — If true, saves as draft instead of sending
• draft — Object referencing a previous draft to replace after sending (with mailbox and id fields)

Attachments

Attachments can be included in the request or referenced by storage file IDs from the Storage API. HTML data URLs may also be extracted into attachments before request validation.

How It Works

1. The API resolves the From address and envelope using the user's account and sender policy.
2. The message is composed using Nodemailer.
3. Unless isDraft or uploadOnly is set, it is submitted to the configured maildrop queue for delivery.
4. A copy is stored in Sent Mail, or in Drafts when isDraft is set, unless a different mailbox is specified or the account is over quota.

Difference from SMTP Submission

Feature	API Submission	SMTP Submission
Protocol	HTTP REST	SMTP (port 587)
Authentication	API token	SMTP AUTH (password/ASP)
Client	Any HTTP client	Email client / SMTP library
Best for	Webmail, integrations	Desktop/mobile email clients

Both paths ultimately queue through ZoneMTA for delivery.