After a mailbox migration from SBS 2003 to SBS 2008, I noticed that the mailbox size limit was set to 2 GB. I removed that limit.
The next day, I got reports that two users were not receiving e-mail, and had this error:
Delivery has failed to these recipients or distribution lists:
The recipient’s mailbox is full and can’t accept messages now. Microsoft Exchange will not try to redeliver this message for you. Please try resending this message later, or contact the recipient directly.
Checking those user accounts, I discovered that the Storage Quota inheritance was disabled, and the users were explicitly set to the 2 GB limit. Those two users were the only ones with mailboxes above that size limit. I had to manually adjust each user’s settings to remove the limits and set the inheritance from the mailbox database settings.
The change did not take effect immediately. I ended up rebooting the server, though it is possible that simply restarting the Exchange services would have done the trick.
Jason (a commenter) pointed out that there is a much simpler and faster way to deal with this than manually adjusting the quotas. It seems that the SBS Console includes a setting for this:
