Mails not being Delivered

[Andy542]

I've been having the above problem - mails are on delivery queue but are not being delivered to the respective domains - and when troubleshooting, I discovered that I cannot Telnet port 25 of my Exchange server from my SMTP server yet the reverse is possible. I use MIMEsweeper for SMTP for SMTP relay.
I have previously even changed the Network card, but this is still persisting.
What may be causing this and how do I sort it out?

Andy

 

[SimonMag]

Does your MIMESweeper for SMTP sit on the same network as your Exchange servers or is it in a DMZ off a firewall? if this is the case I would check that the firewall is allowing port 25 in either direction, as you can telnet from the Exchange server to the MIMESweeper box. I would also check the routing.

Simon.

 

[Andy542]

They sit on the same network. Routing is also fine as in most cases, everything works fine, then all of a sudden it stops working.

Andy