==== Required information ====
- iRedMail version: 0.8.3
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: Ubuntu 12.04
- Related log if you're reporting an issue:
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I have reported this before, and I have checked other posts on this matter, but the solutions given do not seem to work in the long run.

I keep having users which are getting messages that they are 90% and 95% full on their e-mail quota.
They can try to delete messages, either the usual way and emptying the Trash & Deleted Items folder after, or they delete via the SHIFT+DELETE key. But the quota does not change, or it only changes a very small bit like it goes down by 5% to 85% while the use has literally deleted everything and should be at 10%.
I have so far not been able to handle a single user's over-quota-ness, except by giving them more space. Then, after a while, the mail program concedes that it's not over quota any longer.

Is there something wrong with the quota management - I have had this problem with about 25 users so far.

Users are using Thunderbird or MS Outlook. Same problem in both.
Problem is that if a user only has 10% of his quota used, which is easy to verify when he has deleted everything except 5 messages, and the iRedMail quota admin screen still says 87%, then what is the problem?