SMTP port to remote Exchange Server is blocked
Posted on 2010-11-19
We've been having issues receiving email from a specific Exchange server to our Exchange server. Neither server has problems sending to any other server, so this appears isolated.
One thing I noticed is that when running telnet mail.remotedomain.org 25, it does not show any banner. When running netstat it shows SYN_Sent from our server to theirs, but never completes the handshake. From another location, I can telnet ok to the mail.remotedomain.org server just fine.
What might be causing this problem? I can only imagine it is being blocked by the firewall or the IP is being denied by Exchange. I don't have access to the server unfortunately. Anyone have any ideas on what might be causing this?