For users that never login to the webmail there is no visibility when the mailbox becomes full. I suggest doing one or both of the following:
* When the mailbox reaches some configurable percentage full an email is sent to the user as a forewarning. EDIT: Duh, already supported..
* When the mailbox is actually full and mail is being rejected, an email is sent to the user's backup email address if provided.
Otherwise currently the user has no idea that their email are being rejected until someone else tells them which is not at all ideal.
Thanks for your consideration.