I don't mean to stir the pot, but here is my take on this, as the guy who
maintains the installation guides.

When someone comes up with a Windows-based MTA that can deliver mail in a
native manner to LISTSERV's spool directory in the format LISTSERV requires
it to arrive in (JOB format), and in addition can automatically discover
what lists exist on the server without requiring manual configuration of
aliases (as LSMTP can), I will be happy to provide instructions for its
integration in the installation guide, even if we do not formally support
the MTA in question.

That is my understanding of our standard for "turn-key" under Windows (if I
have missed anything I am sure Eric will correct me).  Currently the only
full-featured Windows MTA that fits that description is LSMTP.

I would add that LISTSERV's JOB format is no secret.  The source code for
the lsv_amin (unix) mailer used to deliver mail from sendmail to LISTSERV,
while copyrighted by L-Soft, is nevertheless accessible to anyone who
downloads an evaluation copy of LISTSERV for unix.  I imagine a development
agreement between L-Soft and any Windows MTA developer who wanted to add
native LISTSERV connectivity to his MTA would not be an
impossibility.  (However, I hasten to add that I am only speculating
here.  Anyone interested in such an agreement would need to contact
L-Soft's Software Development department, not me.)

Nathan