We've a problem similar to the question Getting a domain name off of the blacklist but the solutions posted there doesn't help.
The problem I'm facing is that our domain is probably marked automatically by recipient main server as spam.
We've a registered domain and a fixed IP. We're running Exchange 2010, with FortiGate and trial version of MS ForeFront. All was working well until recently when the ForeFront has expired, then we started getting a lot of spam mails. Then the exchange hub transport server overloaded and failed. We can't recover the server immediately, so we setup a temporary hub transport server in the DMZ while troubleshooting the failed one. During this time, our out going mail started to get bounced. Most (but not all) mails are undelivered or goes into spam box of the recipient.
We've checked numerous spam blacklist site, our IP or domain is not listed. We're currently submitting to individual mail server to have us whitelisted. This seems to happen all at the same time, which lead us to wonder if there's a general blacklist which most of our recipient server is checking from. Or there's something which we've overlooked?
The problem stills remains until today which is a week already, and we've since reinstalled the original hub transport. The temporary server is still running.
Btw, the reversed DNS of our IP doesn't match our domain name.
Any help is greatly appreciated.