Problem

I still receive [mailbox-guard] emails telling me my inbox is over quota. But my inbox is empty. What can i do?

Solution

Using IMAP, mails you delete are only "marked as deleted", hence still use disk-space. Often they are just not shown anymore by the mail client. To definitely purge them, follow these steps:

Alpine

Press "X"

AppleMail

After having moved your mails from the inbox to the other folder, as soon as the move is successful, stop and restart Apple Mail.

Thunderbird

Select the mailbox and choose "Compact Mailboxes" from the File menu

Outlook & Entourage

Select the mailbox and choose "Purge deleted messages" from the Edit menu

Eudora

in the Special menu select "Compact Mailboxes" or set your account-properties to automatically purge old mail

http://email.ee.ethz.ch

select "Purge Deleted" in the upper-right-hand corner