Usually, if more than one person is accessing a computer, each user would have their own User Account, which they use a password to access. This is the standard method used on all computers to protect against other people seeing private documents, emails and passwords to mail accounts. Usually, only one User Account is given admin rights and all others are created as ordinary, non admin User Accounts. This means you can set privilege rights for Users. eg: prevent users from installing programs. etc. This User Account password would protect access to their mail account in Thunderbird. Thunderbird would then run in their User Account and create a Profile in their User Account storing all emails that are downloaded to their mail account in their profile and prevent others from accessing their mail account and seeing passwords. I would strongly recommend using User Accounts. This is the best method. If you have one User Account and set up separate Profiles, one for each user and their mail accounts are within their profile. When Thunderbird is started it would ask what Profile to use assuming you have selected Profile Manager to do that. Then there is an addon that can be used to password protect that Profile. However, I must point out that as it is an addon, it can be disabled by anyone with access to that User Account selecting to start Thunderbird in Ssfe Mode.. So, it is really only useful in stopping non technical people or young children. * https://freeshell.de/~kaosmos/profilepassword-en.html There is also a Master Password, which can be set on a profile. This would still allow anyone to see all emails in all mail accounts within that Profile, but it would prevent access to seeing the mail account passwords. If users have their own profile containing their own mail account, a Master Password can be set by them on each Profile. Removing a master password would also remove all stored mail account passwords. See more here: http://kb.mozillazine.org/Master_password