Solution was to edit /etc/mail/sendmail.mc to add RELAY_MAILER_ARGS and
ESMTP_MAILER_ARGS with the correct port number and then to use the '-r'
option of mailx to fake out the sender to an legit address (in my case,
using same address as who I am sending to). Never got to the issue of
dealing with multiple port numbers for different emails as I only needed
the one to get from my 192.168.2.x LAN to pnewell(a)cs.cmu.edu
Thanks to everyone on this list who helped me sort this one out,
Paul