Host Unreachable

[mbrosius]

I am running Microsoft Windows NT 4.0 SP 6a and I have Exchange 5.5 installed on it. I am unable to send email to one domain. All other domains get our mail. I am able to ping, telnet on port 25, and trace route to the domain just fine. I am not blocking any outbound mail on the firewall.

I also have a linux server running sendmail on the same network and it is able to send mail to this domain. Since email to the domain works for this computer, I know that the firewall is okay since both servers masquerade as one external IP address. I am also confident that the firewall on their side is not blocking me due to the masquerading.

Any suggestions would be greatly appreciated. I am out of ideas other than redirecting email to that domain from the Exchange server to the sendmail server but I have been unable to do that either (I'm sure it is because of sendmail refusing to relay).

 

[napoleao]

I had the same problem in my old work and we had the same specifications you mention, I did update Exchange 5.5 with the latest patches and it this solve some host unreachable problems, althought i did foward directly in the exchange server configuration to our second mail server (sendmail) and that did work fine as well. Looks very similar to the problems we had. I cant remember by head now but try to use the foward feature in exchange for the domains you get unreachable and check if it solves anything. I do recomend to download all the latest Exchange 5.5 patches because I think that it may be a bug.