Hello. I've had a recent request to implement the following on a courier server hosting several virtual hosted domains:

1) One of the domains on the server wants to have the incoming email only be able to come in from a third-party spam filtering service that is acting as the public MX. I have the IP ranges of that service.

2) From the looks of it my understanding would be this can only be done on a server-wide basis using smtpaccess, but not have a specific rule so that everything sent to this single domain that is not in that IP range gets rejected. Am I wrong?

3) If my assumption in 2) is correct, my next thought would be to do this on a mailbox level using .mailfilter, where the .mailfilter would match the received from headers against the IP range and if it failed put it in the spam bucket.

Thanks,

Charles Uchu