existing emails are not password protected, password only good to retrieve new emails. If you open Thunderbird and password window appears and hit cancel all existing emails are exposed for viewing

Thunderbird does not offer security for email message content. You could consider setting separate user accounts on the PC or rely on a password to access the PC.

Thanks for your reply David. It would not be difficult for Thunderbird to password emails upon opening Thunderbird without showing existing emails. Perhaps this is something they should consider..Brian

Unlikely. I have been to that well before. Here is some history: https://bugzilla.mozilla.org/show_bug.cgi?id=1566458