It’s unusual for mail servers to suddenly start rejecting messages internally and from external sources. That’s exactly what I saw though over the weekend. A mailserver running mdaemon on Windows 2000 was rejected ALMOST every message that was sent it’s way whether it was an internal mail sender and recipient or external sender to internal recipient. The really interesting things was to see a message sporadically succeed. This problem was with mdaemon, but could have occured with ANY mail server. Here’s why…