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, use "Mailbox->Erase Deleted Items" from the menu or press Command-Shift-Backspace.

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