I have a mailserver, Enterprise Exchange 2003, sp2 that has trouble sending to a few domains. Email gets stuck in queue for retry over and over... to isolate this I created a connector for "problem" domains and specified them, sending this mail through a smarthost that I can control and monitor logs on (an mdaemon server). I can view the logs on the mdaemon server and see a connection from the exchange box, and around 300k gets transferred within 4 to 5 minutes, then there is a connection timeout that occurs. The exchange server is on a 3x3 synchronous connection, the mdaemon server is on a 15x15 synchronous. On the exchange network side there is a barracuda spam filter (for incoming mail only) and a barracuda web appliance (with exclusions for the exchange server). The default gateway for the exchange server is the internet router; no throttling or firewalling done on outgoing traffic on it. Any ideas would be welcome, this has been going on for awhile and we don't seem to be making any progress here. TIA!!