[Mailman-Developers] an opinion about using port 25

[Scott]

Something's been bothering me about the use of connecting to port 25 to
deliver mail.  

The goal of this endeavor, if i remember correctly, was to make
mailman more portable in it's interface to MTA's.  However, I think
that it may well make that problem even worse, and that it lies
outside what mailman should be doing.

Here's the argument:

mailman is a mailing list manager, not an MTA.  If mailman developers
decide to make delivery occur by SMTP, it has to do a LOT of the work
that an MTA should be doing:  queuing messages, retrying every so
often, bouncing messages with appropriate messages under appropriate
circumstances (like deferral messages every 4 hours, etc).  All this
should be the work of the MTA.

I also think that it will eventually exacerbate the problems of
portability.  As a part of test group for a new MTA, and an
administrator of a qmail and a sendmail system, I know many
work-years of labor goes into making an MTA be able to successfully
deliver mail to all the other MTA's out there.   This happens because
different MTAs act very differently.  There are still problems
occuring between code as mature as qmail and other MTA's like certain
microsoft based products (postoffice, LSOFT for nt, etc).

Do we really want to take on that burden?

There are other ways we could pursue this.  There are basically 2
interfaces to an MTA mailman has to consider: updating aliases and
delivering messages.  For each of these interfaces, we could create a
class hierarchy into which mailman's communication with new MTA's
could be easily dropped.  Such a structure, coupled with good
documentation about how to add support for a new MTA seems to me like
it will go further faster than putting a lot of work into SMTP
transactions.   Such an approach could even include smtp transactions,
as a bonus for the daring or those who want mail delivered via a
separate machine than the one on which the list manager resides.  

As far as portability goes, and as far allowing mailman developers to
focus on what a list manager should do, i really think that we would
do better not depending on a universally reliable way of doing smtp
transactions.  

scott