I have a big problem in that my Exchange 2007 server will not send e-mail to any .mil domains. Here is the history of the problem: I originally had an Exchange 2003 server located in the US that we could send e-mail to .mil domains with no problem. We recently moved our mail operations to our parent company in Sweden which runs Exchange 2007. When this happened we could no longer send e-mails to .mil but we can receive from them. When sending the message delays and finally we get a rejection notice - #550 4.4.7 QUEUE.Expired; message expired ##. I originally thought that the recieving smtp servers must be rejecting us due to the fact that our servers are overseas or for some other reason. That does not seem to be the case though. They are telling me that in no way are they blocking transmission from us and reverse DNS is also resolving fine. Their logs show no attempts from us to reach them via SMTP. So now I am back troublshooting the problem on my end. Here is what I have done:
1. Attempted to telnet to port 25 from my mail server to .mil mail server. Connection times out.
2. Verified that DNS is not the issue.
2. Ran a packet tracer from my Cisco 5510. Packet tracer results are that port 25 traffic is allowed to the .mil mail server.
I am at a loss from here. Are there any tools that I can test SMTP communication further to see where the breakdown is occurring?