Hello all.We have an interesting problem on one of our SharePoint farms. The problem is that the outgoing email works most of the time, but a few times a day the SMTP server sends out a bunch of undeliverable notifications. It doesn't happen all of the time, so its hard to troubleshoot. Also, it should NEVER have an undeliverable, because the emails are only sent to an internal Exchange server with known email accounts. Here are the specific symptoms:--SharePoint sends alerts to SMTP server--SMTP server processes the messages most of the time just fine--The SMTP server only sends messages to an internal Exchange server with known valid email accounts--We have the SMTP server set up to send undeliverable messages to an admin account--When the problems occur, they happen in 4-hour intervals which appears to be the maximum time set on SMTP to attempt a redeliver--We can't understand why it works some of the time, but not allThis farm environment:--WSS 3.0 web front end on virtual server (Windows 2003 R2)--Standard SMTP server enabled on web front end--SQL Server 2005 on virtual server (Windows 2003 R2)--All virtual servers created with Windows 2008 Hyper-VDoes anyone know why a standard SMTP server would occassionally not connect to a single internal Exchange server? Any help would be greatly appreciated. Thanks!

Thanks John.SharePoint is sending messages to the local SMTP server. The queue is full of outgoing messages trying to be delivered. There is no specific account created on the local SMTP server, I assume SharePoint is using the administrative account to send. There are no limits set in the SMTP properties dialog box.The local SMTP cannot find our internal Exchange server accounts to deliver some messages (not always). Does that help clarify?Brad