You can display just the basic message header (Date, Address, To, and Subject), or you can display the full message header (Date, Message-id, Address, Reply-To, To, Subject, X-Mailer, Precedence, X-UIDL, and Status).
From the Options and Styles... menu, select Preferences under My Options.
On the User Preferences page, locate Display Message Headers and select Basic or Full.
Click the Save button at the bottom of the table you are working in when finished.