[Dovecot] negative quota usage causes over-quota messages with dictionary quota backend

[Marshal Newrock]

Using dovecot 1.0.rc21, with quotas being stored in mysql, I have found
that if the quota usage stored is negative, then when a message is
given to dovecot deliver, the account is reports as being over quota.
The squirrelmail quota usage plugin says that the quota is at around 40
million percent (I should have written down the exact number), though I
don't know if that's squirrelmail or dovecot coming up with that
number.  At a guess, I'd say there's an unsigned int being used where
the result can be signed.

I'm using MySQL 5, so for an easy workaround, I added a trigger that
sets the quota usage to 0 if it goes less than 0.  I could probably
also set the field to unsigned int, but I haven't tested what mysql
does if you try to change an unsigned int field such that it would be
negative.

-- 
Marshal Newrock, Ideal Solution LLC
http://www.idealso.com