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
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:
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