I found how to change the sending port:
http://sendmail.org/faq/section3.html#3.39  (Duh.  Going to the project
documentation instead of wading through Google search hits.)

Now to understand the authentication part...

It appears that the access.db (and therefore access) file is involved
with storage and use of authentication information.  I said I was going
to drop this till another day but I hate leaving stones unturned.

Alan