We setup a spam filtering box as the first stop of incoming email of our company. Our outgoing emails are being handed by another exchange box.
The spam filtering box has a mx record on the public dns server.
One of our vendors is saying they cannot receive email from our domain at all. They told us they have put our domain name into the whitelist of their spam filter.
When we tried to telnet to their domain from our outgoing exchange box via port 25, connection is being rejected right the way.
What could be wrong? Is it ourside or theirs