Thus said Ken Hornstein on Tue, 17 Aug 2021 21:01:18 -0400:
587 is the port that is supposed to be used by MUAs to submit mail.
nmh is a MUA; it seems perfectly logical to me that the default that
is used by nmh is the submission port.
Yeah, I can see your point though I still think it was an abrupt change
[though in light of the dwindling number of nmh/exmh users perhaps it's
perfectly fine for the community]. Fortunately I haven't been impacted
by this (I would know because I don't run anything on port 587) so I'm
really arguing more out of principle of least surprise than anything. I
prefer to use "sendmail/pipe" for the mts setting which then allows me
to easily use scripts to filter emails as they are submitted.
Sure, that could also be done with an SMTP server, but it's much easier
with a pipe.
Andy