Summary: Messages sent to a relay server (Surgemail) would often have messages not get delivered. Messages were being delivered through an ASP application. However some messages would go through. Performing a telnet session works fine. When checking the SMTP logs the client would issue a rset command after the RCPT TO: command. The SMTP server (surgemail) would reply with an recipient ok and would be received by the client.
The cause was Symantec AntiVirus 10.0.0.359 running the Internet E-mail Auto Protect. Disable the feature.
James Chong (MVP)
MCSE | M+, S+, MCTS, Security+