I have been experiencing an issue on my SBS 2003 server of messages getting stuck in the queues. When users send email to firstname.lastname@example.org, email@example.com, or firstname.lastname@example.org, the messages get stuck in the queue. If they send email to anyone else, it is delivered just fine. If I reboot the SBS server, these queues are cleared out and the messages in them are delivered without any issues.
Any ideas on what may be causing this?
Regards and Happy New Year,