I first suspected that somehow we had ended up on an RBL. Well, we had but it was one of those that blocks blocks of addresses (in our case the whole Class C we are on) and thus is little used, since it blocks many valid addresses. During this period of discovery, I found our rDNS had vanished, which was requested, and done, to be replaced, but no explanation as to why it had vanished–I suspect a tech made an error. Even so, we are still having the problem.

We are now discussing building a new server, but are unsure if this will resolve the issue, and are hesitant to put the time and money into buildin g a new server if we do not have to.

We have done, among other things, turned off the A/V even though the Exchange directories were excluded from scanning, changed the public IP address, check to ensure no changes had been made between working and not working (when every one is a tech . . .), scanned everything wxcept the Information Stores, with two A?V products other than what we use (clean), and still no joy.

Does anyone have any ideas?