The LMTP can be used to transfer mail from sendmail to the program that delivers mail to the local user. Historically, that has been a program, such as /bin/mail, that simply gathered a message on its standard input and wrote that message to the end of the file that the user read. Beginning with V8.9, sendmail can speak the special LMTP language to local delivery programs. The mail.local program (Section 5.3), supplied in source form with the sendmail open source distribution, is one such program.

Operating systems that can use that program for local delivery are already set up correctly to use it. Those that are not already set up to use it can use this feature to override the settings in their OSTYPE (Section 4.2.2.1) defaults.

Building and using mail.local is described in Section 5.3. Once it is built and installed, you can use this local_lmtp feature to enable use of that program. One way to do that looks like this:

FEATURE(`local_lmtp')
MAILER(`local')

Note that this feature must be declared before you define the local delivery agent. This feature defines both the use of mail.local, and the place where that program can be found. By default, that location is /usr/libexec/mail.local. If you installed mail.local in a different place or under a different name, you can specify that location like this:

FEATURE(`local_lmtp', `/usr/sbin/mail.local')
MAILER(`local')

This feature also sets the LOCAL_MAILER_FLAGS (See this section) to a default of F=PSXfmnz9, sets the LOCAL_MAILER_ARGS (See this section) to a default of mail.local -l, and sets the LOCAL_MAILER_DSN_DIAGNOSTIC_CODE (T=) to a default of SMTP. If you need to change any of these, you can do so with the proper mc macro. Just be sure you make all your changes after the local_lmtp feature was declared, and before the local delivery agent is declared:

FEATURE(`local_lmtp')
                         define your new values here
MAILER(`local')