sendmail, 4th Edition

FEATURE(no_default_msa)

Disable automatic listening on MSA port 587 V8.10 and later

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 connecting to that port.

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

FEATURE(`no_default_msa')

Additional information about MSAs can be found in our discussion of the DaemonPortOptions option (DaemonPortOptions on page 993).

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

Be aware, however, that this feature also disables the listening daemon on port ...