I posted a sendmail problem last week, explaining most mail on a new
Fedora server gets trapped in the mail queue, marked with a deferred
connection status. Once and a while some messages will be delivered after
a reboot, or a reboot of the firewall. I decided it was a firewall issue,
so we did a new install of IPCop 1.46. I still have the same problem, so I
uninstalled and reinstalled the sendmail rpm, and removed the loop back
statement in the m4 file. In a shell I can ping any domain from the mail
server, and I can telnet to the server via port 25, getting the welcome
banner. However, I just tried the reverse; attempting to telnet to a
working mail server on port 25 from the problem box. the telnet command
hung, and never did make a connection to the other server. this was done
with IPtables disabled.

Any ideas what to look for?