more on e-mail password

one of my problem was solved here, but...Netscape e-mail password protect me only from downloading by someone else my new messages (when you click "Get New Message ", that password window pops-up)...so all my saved, sent etc. messages are wide open...obviously, i could delete "sent ", move "saved" somewhere else, etc. but it is a hard way...i wonder if there is any way to require a password just to open my e-mail agent....sorry if i'm annoying :-( ....thanks for any help
Broni