Editing Local Mail Transfer Protocol (section)

==Differences from SMTP==
LMTP conversation syntax is based on the same commands as SMTP (formerly called Extended SMTP) with the following exceptions:<ref name="rfc" />
* LMTP must not be used on port 25, reserved for SMTP
*LMTP uses <code>LHLO</code> verb instead of <code>EHLO</code> or <code>HELO</code> used in (E)SMTP
* ESMTP requires a single status for the entire message body. LMTP requires a response for each previously successful RCPT command. That is, in case of multiple recipients, after the body of the message has been transmitted, LMTP can still fail for some recipient while succeeding for the others. With this facility, LMTP can fail if a user is over quota without the burden of generating [[bounce message]]s.

The key difference is that LMTP will reject a message for a specific final recipient if it is not immediately deliverable. This removes the need for a mail queue. For this reason, LMTP is not run on the standard TCP port of SMTP.