Go to '''[http://kb.mozillazine.org/Menu_differences_in_Windows,_Linux,_and_Mac Tools|Options]|Security|Passwords→Saved Passwords''' and delete everything. You could set a Master Password. Then you'd have to enter that before being able to send or get new messages. Bear in mind that once you have "logged in", Thunderbird remains able to connect for the rest of the session, that is, until you close it. Many users ask about a password and don't seem to worry about what happens when they go away and leave the computer unattended. That's where a system-wide password, usually associated with a screensaver, or in the extreme, logging out, come into play. In which case, individual email account passwords are somewhat irrelevant. None of these Thunderbird passwords stop an interloper from opening Thunderbird and viewing old messages. Some guidance on making Thunderbird secure here: http://kb.mozillazine.org/Protect_the_profiles_contents I use the Startup Master add-on because it doesn't display Thunderbird's contents at all until the correct password is entered. This doesn't cover what to do when leaving the computer (I use Window's screen lock winkey+l) nor the fact that a savvy user could start Thunderbird in Safe Mode and disable the add-on. Over and above all this, note that Thunderbird's message store is effectively plain text and visible to anyone who can access your file system.