Delivery Properties

If you want Mail Tool to automatically display the headers for incoming mail messages, check the Automatically Display Headers option. If you do not choose this option, Mail Tool does not display headers for incoming messages unless you specifically request them by choosing Load In-Box or Save Changes from the File menu.

If the Show "To: recipient" ... option is checked, the Mail Tool header of a message sent by you will display the recipient of the message instead of your mail address.