cPanel E-Mail Disk Usage Issue

In one of my hosted account Email of my VPS, I am experiencing actual disk usage related issue of my e-mail accounts. Using cPanel, two of my e-mail accounts are showing following disk usage: "farid" email account - 537 MB "info" email account - 2.15 GB But when I contact with my VPS provider then have provided me following disk usage report of those email account: root@vps [/home/erfbd/mail/erf-bd.com]# du -h --max-depth=3 16K ./farid/mailboxes/Archive 20K ./farid/mailboxes/spam 52K ./farid/mailboxes/Drafts 48K ./farid/mailboxes/Sent 36K ./farid/mailboxes/Trash 556K ./farid/mailboxes/INBOX 732K ./farid/mailboxes 1,9G ./farid/storage 1,9G ./farid 16K ./info/mailboxes/Archive 60K ./info/mailboxes/spam 44K ./info/mailboxes/Drafts 436K ./info/mailboxes/Sent 48K ./info/mailboxes/Trash 980K ./info/mailboxes/INBOX 1,6M ./info/mailboxes 5,2G ./info/storage 5,2G ./info They were unable to provide me the actual reason for this and inform me to contact with cPanel directly. Need your support.