You may change whether or not e-mail sent or received, by you, to and from contacts, is publicly available by default in the following way:
From within Mail mode, select Preferences from the Options menu. The Preferences dialog box is displayed. Select the Access page.
E-mail sent from now on may be made publicly available, by default, by selecting the Sent and received mail is publicly available to all users by default radio button. Selecting the other radio button will make all mail, sent or received from now on, private to you by default.