I wanted to mention that when using qmailadmin-1.12 and vpopmail-5.3.18, if I set the quota from qmailadmin to 100MB, the quota is set to 100483292.00 (I'm just guessing on the bytes, but you get the idea).
For some reason, I belive the .00 makes vdelivermail bounce email saying the user is over quota. Using vsetuserquota to set the actual # of bytes works fine though. Rick