The LMTP class

RFC 2033 defines the Local Mail Transport Protocol. In many ways, this is very similar to SMTP, but with no guarantees of queuing. It is, in a sense, an alternative to ESMTP, and is often used for local mail routing (e.g. from a Mail Transport Agent to a local command or system) where the unreliability of internet connectivity is not an issue.

The LMTP class subclasses the SMTP class and its only functional difference is that it implements the LHLO command, and prohibits the use of HELO and EHLO.