I'm trying to get mailbox quotas to work but I'm unable to do so. I'm using virtual users with mysql authentication:

Here's the pertinent lines in my main.cf

virtual_mailbox_limit = 51200000

virtual_create_maildirsize = yes
virtual_mailbox_extended = yes
virtual_mailbox_limit_maps = mysql:/etc/postfix/mysql_quota.cf
virtual_mailbox_limit_override = yes
virtual_maildir_limit_message = Sorry, your message could not be delivered. The user you are trying to reach has reached his mailbox size limit. Please try again later.
virtual_overquota_bounce = yes

Here's the mysql_quota.cf file:

user=mail
password=somepassword
dbname=maildb
table=users
select_field=1024*1024*quota
where_field=id
hosts=127.0.0.1

I set one of the users with a quota of 1 in the database and I know for a sure this user has well over a 1MB of mail but there is never an indication that the quota limits are working. Mail is getting delivered to this user and no notification ever goes out that the mailbox is over it's size limit. I'm under the understanding that the VDA postfix-2.1.5-trash.patch.gz is required for the quotas to work and it's my understanding that the libpostfix1 package contains the postfix-2.1.5-trash.patch.gz and it already installed on my system.

Also, I'm a little confused on the "virtual_mailbox_limit = 51200000" and
"virtual_mailbox_limit_override = yes" lines. Is the "virtual_mailbox_limit = 51200000" the global mailbox limit size for ALL mailboxes? And what exactly does the "virtual_mailbox_limit_override = yes" exactly do?

Yet, the the quotas are not working.

At the back of my mind, something tells me that Postfix doesn't handle quotas for maildir style mailboxes properly. Not a lot of help, but as they say, every little bit...