[NTLUG:Discuss] Can sendmail listen on multiple ports?

[Egome]

Some isp's are filtering packets outbound on port 25.   OK..well it's ONE
isp in particular who shall remain nameless but whose initials are
B.I.G.P.L.A.N.E.T.

At any rate, when the user is on the road, he cannot contact his mail server
(or any other mail server) to send his mail.  The ISP's mail server's won't
relay his messages because the return address is different from his isp
email account.

sooOOoOOooo, if I could make sendmail listen on ports 25 AND say...2525, we
could BYPASS the SMTP filter.

So, can it be done?  I have yet to find out how to make it listen on BOTH
ports?  Am I missing something?

-Richard