I am confused. You say the account was removed, yet you state that the account can't be deleted. If thunderbird is still prompting for the password, then something is still there, possibly a calendar?

Hi, thanks for the reply.

I removed the account from thunderbird. Long time before the password loop started. There is no connection left (no calender nor else).

I just mentioned that I cannot delete the email adress itself if this was going to be one of the proposed solutions. This email adress is being used by other people.

Just a thought: click account setting, and scroll down left side to 'Outgoing Servers SMTP' and see if there is a server there for the deleted account.

Hi, Yes, there is. I use another email address from the same email provider.

I just removed the second server but the loop continues.

If the account authentication is set to oauth, you may also need to delete the oauth tokens in password manager.

Hi, the account is completely removed from thunderbird but there is still the password loop.

Bevor the removal, the authentification method was not set to "oauth" but to "password, normal".