PMTU probing?
why should PMTU probing take several minutes? especially between a
firewall and the SMTP server inside the firewall, on an already-
established connection?
Unless the firewall is busy handling Code Red analysis -- which is
pretty likely right now, by the way -- this was the only thing that
comes to mind as something I have seen take awhile. If ICMP 'must
fragment' messages are being dropped, the TCP stack has to decide
its dealing with a broken network and start experimenting with
smaller packets.
-d