LMTP

LMTP , or Local Mail Transfer Protocol, is a derivative of SMTP , Simple Mail Transfer Protocol . LMTP is designed as an alternative to SMTP in situations where the receiving party does not use a message queue, for example, a mail storage server operating as a Mail delivery agent . This is desirable due to the fact that in this case it is enough for the mail storage server to manage its own mail storage without using additional space for the message queue. SMTP does not provide this feature because a single message can have multiple recipients. SMTP can determine whether a message is sent successfully either to all recipients or to none of them, thereby requiring a separate queue for recipients whose message transfer failed. On the contrary, LMTP allows you to determine the success of the transfer separately for each recipient, thus the message queue can be supported on the client side. A typical client in this situation is Internet access to the mail gateway. LMTP is not intended for direct use in a wide area network .

LMTP is an application layer protocol that runs on top of TCP / IP .

An LMTP session consists of the same commands as ESMTP, with the following exceptions:

• EHLO team replaced by LHLO
• ESMTP requires a single response from the server on the status of the entire message after the client has finished sending the DATA message. LMTP requires a response from each successfully completed RCPT command.

The key difference is that LMTP will reject the message if it is not possible to send it to the final destination immediately. This eliminates the need to maintain the queue. Therefore, the LMTP server on the TCP / 25 port cannot be considered valid.