How do I delete a message in IMAP?

Select the message in the message list and click the Delete button on the toolbar. The message you want to delete is marked.

In the Edit menu, choose Purge Deleted Messages to remove the deleted messages from the folder permanently. Once you have permanently deleted a message, you cannot recover it.

If you want to restore a message that has been marked for deletion on an IMAP server, choose Edit/Undelete.

If you want deleted messages to be purged automatically, choose Tools/Options/Maintenance tab and tick the box Purge deleted messages when leaving IMAP folders. Purging only happens when you are connected to the internet. If you are not connected, the messages are permanently deleted when you are back online.