Problem Description
- When logged in to webmail, the mail quota or amount of storage used, is not showing at the bottom of the list of messages
- If your mail app supports viewing quota, it is not showing the total amount of storage used (note: not all mail apps support this function. Apple Mail does)
Problem Resolution
If you have your own VPS or a Plesk Reseller account and the mail account has its quota set to unlimited, you will not see the quota in any mail interface, including webmail, because there is no limit.
In all other cases, reloading the IMAP server, then waiting about 2 minutes should resolve the issue. To force a reload of the mail server and your account's configuration, change the mail quota in Plesk to be somewhat smaller than the current limit, save changes, then put it back to default and save your changes again.