Large files filling Up HDDs?

==== Required information ====
- iRedMail version: 0.8.6
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): mysql
- Linux/BSD distribution name and version: centos 6,4
- Related log if you're reporting an issue: -
====

I'm having some difficulty locating any large files that may be taking up space on the HDD's.

This is mostly due to my /var/vmail/vmail1/ being very large.

I've only been able to find 2 major sources of disk consumption, those being:
/var/vmail/backups/mysql/*
and
/var/log/*

Is there anywhere else that large files are being stored? We keep running into HDD space issues but I can't seem to locate the source of the issue.