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.