A Couple of companies that we regurlarly recieve mail from now route
there mail through a company called messagelabs.
Any mails now been recieved from messagelabs are Timing out.
Using IIS on a Relay PC.
See Logs below
2006-03-03 00:12:35 193.109.255.100 mail24.messagelabs.com SMTPSVC1
RELAY4 192.168.*.* 0 HELO - +mail24.messagelabs.com 250 0 SMTP - - -
2006-03-03 00:12:35 193.109.255.100 mail24.messagelabs.com SMTPSVC1
RELAY4 192.168.*.* 0 MAIL -
+FROM:<61826.172773302@ems.euromoneyplc.com> 250 0 SMTP - - -
2006-03-03 00:12:35 193.109.255.100 mail24.messagelabs.com SMTPSVC1
RELAY4 192.168.*.* 0 RCPT - +TO:<user@mydomain.com.COM> 250 0 SMTP - -
-

Timeout:
2006-03-03 00:35:17 193.109.255.100 mail24.messagelabs.com SMTPSVC1
RELAY4 192.168.*.* 0 TIMEOUT - mail24.messagelabs.com 121 635564 SMTP -
- -
2006-03-03 00:35:17 193.109.255.100 mail24.messagelabs.com SMTPSVC1
RELAY4 192.168.20.*.* 0 QUIT - mail24.messagelabs.com 240 635574 SMTP -
- -

Any Help would be great.

Anyone ???

[quoted text, click to view]

Okay, that's pretty precise. If these are the only timeouts in your
logs, start looking at tracerouting to the connecting IPs from your
mailserver, and running a network sniffer to look for errors.

Sorry I can't be more directly helpful, but the actual timeout is
almost certainly happening outside of SMTP, either some weirdness with
the local TCP/IP stack, router MTUs, stuff like that.

You could also temporarily increase the IIS connection timeout and see
if, for some reason, these sessions are inactive fot just over the
timeout threshold.