When I start Thunderbird I get the login box. If close it or just ignore it I still enter Thunderbird with full access to the accounts.

You cannot send or receive new messages without providing the account password.

Thanks for your quick reply.

Not being able to send or receive is great - but I don't want anyone reading even the subject line of existing emails.

Tony, I don't think you have the right expectation of what a desktop mail client program such as Thunderbird does. It isn't a web program that you log into. It downloads your mail when it logs in to the server and makes it accessible to you on your own computer even when you are not connected to a server, and it allows the mail to be deleted from the server and you can still have a copy. So you might need to log in to the server (I have mine set to do so automatically, so I don't need to remember passwords), but the client is your own program with your own copies of the mail. Anyone with access to your desktop should have access to the client, then. If you need additional security, you need to log out the desktop when you aren't using it. Or maybe if that isn't enough perhaps you can create a virtual machine that requires a separate login and move the mail client (T'bird) there.

I don't want anyone reading even the subject line of existing emails.

See http://kb.mozillazine.org/Protect_the_profiles_contents

Thanks for the explanations, I do understand it is a client, and the way clients work - but my point is that when opening the program a password is required, yet I have found if I close the input box without entering a password the program works as usual making the password redundant. I do realise that extra security could be used by me, and it is a tiny issue for almost everyone else, I suppose it is just a niggle and is not a world-ending problem.

I think I will tick that the issue is solved, as I expect it it would be for people without my OCD problems! I don't want to waste people's time, there are better things to worry about than this.

Thanks again, Tony

The password is not required to use T'bird! I use it and haven't typed in a password for a long time. The password is being fed through T'bird to the mail server that it's trying to connect to. That needs the password. In Server Settings you probably have "Check for new messages at startup" checked, which is normal. And you aren't asking it to save the password. I do save my passwords (I can see them in Options -> Security -> Passwords) but they're separate for each server I connect to. So when you start the program, it immediately tries to fetch the mail and asks you for your POP or IMAP server's password. You presumably only have one, so you're confusing its password request with T'bird's wanting a password to start up.

Well that confuses me even more! I have half a dozen email accounts, IMAP and POP3, but none of them use the password I use when I start the program. Each email account has a different password, these are all saved in Thunderbird. Some of the accounts are set to download on opening the program, and some, that I hardly ever use, need me to select "get messages". But reading your reply has reminded me that I have a Master Password set, that is what I have to put in the text box when I start Thunderbird, and in Options it says a master password protects all the other passwords. It then follows that as you have said I do not need to use a password to start the program - but without entering the master one to "unlock" the email account passwords I assume I can see the ones already downloaded but can not download or send any more. So - All sorted, now I understand. Thanks.