This problem occurs when you use a Microsoft Entourage for Mac client to send a recurring meeting request to a Microsoft Exchange Server 2003 resource mailbox, because Microsoft Entourage for Mac cannot send valid location information to Exchange 2003. Therefore, Exchange 2003 automatically declines the meeting request. See ME933093
for a hotfix applicable to Microsoft Exchange Server 2003.
This problem occurs if you delete a mailbox before you delete the Auto Accept Agent event sink for the mailbox. In this situation, the mailbox is deleted. However, the mailbox is still registered in the store events folder. Therefore, an orphaned entry for the deleted mailbox is created in the System mailbox. See ME920861
for details on solving this problem.
In our situation, the mailbox quota caused the problem. Mailbox had 102MB in size, while system policy limited this mailbox store to 100MB.
When I sent an invitation to a meeting, I received a confirmation mail from the friend but I did not receive any confirmation from that resource mailbox. At the same time new Auto Accept Agent errors appears on server. This happens because quota is exceeded, generic mailbox cannot send confirmation and the error is generated.
In our situation, we applied Mailbox Manager Settings for generic mailboxes and cleared them.
This behavior manifests when Resource Mailboxes are no longer being managed by Auto Accept Agent on Exchange Server 2003. Unbind each Resource Mailbox using RegisterMailbox.vbs with the /U switch then reregister each Resource Mailbox using the same command without the /U switch.