To delete a message from an IMAP account
  1. In the message list, select the message.

  2. On the toolbar, click the Delete button. This marks the message you want to delete.
  3. On the Edit menu, click Purge Deleted Messages to remove the deleted items from the folder. Once you purge a message, it cannot be undeleted.

Notes
Related Topics

Delete a mail message

Delete a message from an HTTP mail account

Move or copy a message to another folder