FuBar MailExpiryFu is a FuBar addon that will display when the oldest mail item is due to expire for your alts, and how many items are in each mailbox.
It will be useful for making sure you clear out your mailbox before items get returned to the AH or alts.
You must visit the mailbox for an alt before it can start keeping a track of the oldest mail item.
MailExpiryFu will detect mail being sent to alts.
MailExpiryFu will try to differentiate between regular mail, and pending AH sales.
MailExpiryFu will try to detect incoming mail and increment counters accordingly.