Every time I open my e mail it wants a user name and password

- What version of Thunderbird?

- What is your operating system?

- Who is your email provider?

- Is this an IMAP account or POP3?

- What error messages do you see? Please quote them precisely and in full. Screen shots would suffice.

- When you say, "open my email," do you mean when you open a message that's already been fetched, or when you first start the program, or what? Does it happen when you send a message?

- Did this just start or has this been going on for a while? Did it coincide with a Thunderbird or operating system update?

What version of Thunderbird? 140.12.1esr (64-bit) What is your operating system? Windows 10 Who is your email provider? 140.12.1esr (64-bit) Release notes Thunderbird Windows MSIX packagethunderbird-MSIX - 1.0

https://1drv.ms/w/c/e2cc170239338a99/IQABOwHDhDUdRKo5Wze0IROrAX5bgLyDU13mIp6qMAawf-w

That appears to be asking for a password to grant access to a calendar hosted on iCloud, not for an email password. Is this something you need? If no, just unsubscribe from Thunderbird's Calendars window. If you do need it, iCloud may need some special steps done to authenticate. I'm not familiar with their service, but this article I found:

https://cli.nylas.com/guides/icloud-caldav-settings

seems to suggest that you will need an "app password", which would be obtained from Apple/iCloud and would be separate from your other passwords.

(btw, your email provider would be the company that hosts your email account (iCloud?) not Thunderbird.)