Deleted IMAP email is just crossed out, not deleted.

[jamesh]

In the IMAP standard, when you 'delete' an item, it isn't actually deleted permanently. Instead, it's simply marked as 'deleted'. This is often displayed in email clients as a crossed-out email. It's merely been flagged for deletion. To actually delete the item permanently, you have to 'purge' the mailbox. Most IMAP clients have an option in one of the menus or on the toolbar called 'purge'.

Unfortunately, most people are used to the Macintosh and Microsoft model of 'delete means move to Trash'. So in our webmail we have emulated this. When you delete in our webmail it does the following: Copy message(s) to Trash, mark for deletion, and purge the mailbox.

In Outlook and Outlook Express, you can uncheck View->Current View->Show Deleted Messages to hide deleted but not-purged emails. Or if you'd like your deleted messages to be visible but grouped seperately, select View>Arrange By>Current View>Group Messages Marked for Deletion.

In Thunderbird, by default deleted messages are automatically purged to the Trash.