Got this issue on 2 servers now. SBS 2003 Std SP1 with Exchange 2003 SP2. Both server have mail delivered direct to fixed IP but also collect some mail via the POP Connector. Periodically the Messages Pending Submission queue "sticks" and accepts new messages but does not submit them. Consequently noboby gets any mail from this point on, either via POP or direct. When this happens if I try stopping the SMTP service it fails to respond and the only recourse is to bounce the box, which works, but I need to find out why the queue is periodically locking up.