When you delete a message in your IMAP inbox, it isn’t removed. Instead, it is displayed using stikethrough text. IMAP folders require purging for the removal of deleted items. To manually purge your IMAP folder, follow these steps:
1. Select an IMAP folder such as your Inbox.
2. Click Edit and mouseover Purge.
3. Select to Purge from the selected folder, from the current account, or from all IMAP accounts.
4. When the confirmation box appears, click Yes.