At our company we have starting getting a problem with spam maessages. Although our inbound e-mails are scanned by an external company first and then forwarded on, an examination of the headers of the spam reveal that they are bypassing the scanning at appearing directly on the public address of our Exchange 2000 server. I have the IP addresses of the external filters so in theory what I need to do is block all inbound SMTP traffic at the firewall unless it is coming from these two addresses.
However for operational reasons, I'd rather get the Exchange server to do this if possible. I don't mind what happens to mail from 'unwanted' addresses as long as the SMTP packets get dropped. Is it even possible to do this from within Exchange and if so how?