If your email account is reporting that you are over quota, but cPanel says you have used 0MB then please try the following steps:
- Login to cPanel
- Go to the Email Accounts page
- Reset the quota again
If this does not correct your issue, please visit the following location using FTP or cPanel file manager:
/home/username/mail/domain.com/emailaccount
Now remove the following files (if they exist):
maildirsize #quota storage
Now repeat the steps above to reset the quota, this should recreate your quota files with the correct data.