I have a customer that all there outgoing exchange mail has stopped. I have mixed errors. Some show that I may have been blacklisted and others show I may have been attacked by a virus through the NAT port 25. I get the " You do not have permission to send to this recipient" and domain.com #5.5.0 smtp;550 Mail from (server IP Address) refused. I checked with some blacklist websites and they say I am not listed and the CBL site says I am. Can anyone make heads or tails. Ran scans on all stations and the server and found no virus's.