You're talking about Windows accounts. How is that related to Thunderbird?

Thank you for your reply. Indeed I am talking about Windows7 accounts. The password protected Administrator account which I have never used, except to create a Standard account, without password since I am the only user on my laptop, and which I use all the time. Now how does that relate to Thunderbird. I have started using a new Windows application which seems to require administrator user privilege. Therefore at the moment I am spending most of the time on the Administrator account. Now and then I also use Thunderbird on that account, although I normally use Thunderbird on the Standard account. Now I am surprised to see the same Thunderbird e-mails on the Administrator account that I also see on the Standard account. What can I do to prevent this unnecessary duplication? Thank you

I have started using a new Windows application which seems to require administrator user privilege.

Have you tried to start the app requiring admin permissions using 'Run as Administrator' from the unprivileged user account?

Now I am surprised to see the same Thunderbird e-mails on the Administrator account that I also see on the Standard account.

I'm still struggling to understand how this is a problem. You've set up the same email account in two instances of Thunderbird (for the Administrator and for the unprivileged user). Technically this means Thunderbird creates a profile for each Windows user account. These profiles are independent from each other. Even though there are some dependencies to account type (POP or IMAP) and server settings, receiving the exact same email messages for the very same email account in both profiles would be exactly what I'd expect.

Thank you for your reply. You are right, Thunderbird doesn't care about Windows user accounts. Each time a Windows user account starts Thunderbird for the first time, Thunderbird simply creates a new profile, and that's it.

I found the answer to my question by disabling the following Server Settings: Check for new messages at startup Check for new messages every xxx minutes Automatically download new messages

Once again thank you