[Dovecot] Maildir++ quota: When is it recalculated?

[Ulrich Zehl]

We use Maildir++ quota, with the rules taken from our LDAP backend. We also
have an old expunge script that's not quota-aware; it removes old messages
from the maildir by simply deleting the files.

Sometimes, a mailbox is over quota before the script runs, but well under
quota after the old messages are deleted. This change does not seem to be
picked up, however: When I try to deliver a new message (using Dovecot's
deliver), the attempt fails with an "over quota" error.

I tried finding out from the source code whether this is intended behavior,
but unfortunately, I'm not enough of a programmer, so I have to ask here:
Should I be able to delete mails from a maildir, and expect the quota
plugin to notice the change?

We use Dovecot 1.1.8, by the way.

Ulrich