Our Ironport Spam Filter has come up for renewal and we are wanting to entertain other options. The problem that we are having is that Exchange seems keyed to only accept incoming mail from the Ironport. We are testing out Mail Cleaner Community Edition and have tried giving it the IP that the Ironport had.
It can receive mail from our Firewall just fine, but it cannot pass that mail to the Exchange Server. We have tried disabling all AV protection on the Exchange Server and that has not helped. It seems like it is hardwired to only accept mail from the Ironport by some identification other than IP. Where would such a setting be?