Scenario : Your mailboxes are overquota and you clean the old emails to make space. Cpanel shows no reduction in mailbox size still.
Problem : Actual mailbox Size : 20MB. Cpanel Shows : 70MB. Cleaning up the mailbox doesn’t help.
It happens because of a corrupt maildirsize file. maildirsize file holds the information about the total quota of a mailbox and the actual size information too. This file is supposed to be periodically updated automatically.
Solution : Reset your maildirsize file. If you have SSh access, you can delete it easily. If not, you can login to your ftp client using the admin username and password, it gives you access to root directly. Look for /mail/domainname/emailaccountname/maildirsize file and delete it.
Reset the mailbox quota again, so the maildirsize is again recreated automatically.