quota irregularities

A user has suddenly exceeded their disk quotas, literally overnight. I recommended for them to empty/purge their trash folders, but the problem remains. After looking at the Mail and FTP Users overview, I noticed that there is a very large difference between the mail file size and the quota used.

Quota Used | Mail file size
114.05 MB 16 kB
59.88 MB 944 kB
40.07 MB 10.52 MB
4.10 MB 1.24 MB
21.35 MB 472 kB
252 kB 204 kB
276 kB 212 kB
13.36 MB 504 kB
27.77 MB 10.36 MB
18.57 MB 468 kB

This doesn't make sense to me that the directory can be full even though there is very little mail in their inbox. Is this normal? What can I change/delete to reduce the used quota?

Status: 
Closed (fixed)