http://www.rfc-editor.org/rfc/rfc4468.txt
RFC 4468: Message Submission BURL Extension, C. Newman2006-05-01T23:00:00-00:00The submission profile of Simple Mail Transfer Protocol (SMTP) provides a standard way for an email client to submit a complete message for delivery. This specification extends the submission profile by adding a new BURL command that can be used to fetch submission data from an Internet Message Access Protocol (IMAP) server. This permits a mail client to inject content from an IMAP server into the SMTP infrastructure without downloading it to the client and uploading it back to the server. [STANDARDS-TRACK]