When V8.10 sendmail starts up in daemon mode, it listens both on the normal port 25 for incoming SMTP connections, and on port 587 for the local submission of mail. This later role is that of an MSA (documented in RFC2476).

Although listening on another port by default might seem like a bad idea, it is actually a very good way to enable a smooth transition to the adoption of MSA services. The MTA, for example, when listening on port 587 will limit the amount of automatic canonicalization it does on unqualified addresses. This is good because that canonicalization is really the role of an MSA.

Although we highly recommend you leave this service enabled, you might prefer to disable it. If so, you can disable it with this no_default_msa feature:

FEATURE(`no_default_msa')

Additional information about MSAs can be found in our discussion of the DaemonPortOptions option (DaemonPortOptions).

Because there is no way to directly change the settings of the MSA in your mc configuration file, you can use the following trick if you need to change, say, the M= equate from M=E to M=Ea:

FEATURE(`no_default_msa')
DAEMON_OPTIONS(`Port=587,Name=MSA,M=Ea')

Here, this no_default_msa feature prevents the automatic creation of an mc configuration entry for an MSA. You then insert your own declaration, with your new settings.