[Evolution] Still having trouble configuring evolution to use outgoing mail server at port 587

[Leonard Evens <len math northwestern edu>]

I have been trying to (A) configure my office machine (using RedHat) to 
act as an outgoing mail server using port 587 and (B) to configure 
evolution on my home machine (Fedora 11) for sending email through
my office machine.

I think I've managed to configure sendmail.mc on the office machine
to use port 587. 
nmap office-machine
run on my home machine yields (among other things)
25/tcp    filtered smtp
587/tcp   open     submission
(I need the 25/tcp so my office machine continues to accept other
incoming mail so as to act as a mail transfer agent.)

But I can't configure evolution to send mail using my office
machine.  Nothing I try works.

I have been  using comcast's outgoing mail server at port 587
for a while now, but the same evolution settings don't work for my
office machine.

Can anyone suggest what to do either at home or at my office?
-- 
Leonard Evens len math northwestern edu
Professor Emeritus, Department of Mathematics, Northwestern University