please post a screenshot at the point where you get the error.

I actually think it might be a password issue. I didnt set the email up initially but I did get the passwords from thunderbird saved passwords but at the initial stages it says password not recognised when I try offline as per one of the suggestions from the support forum.

Try setting up the account offline: checkmark File/Offline/Work Offline, then File/New/Existing Mail Account..., enter the correct settings manually, Click Done to close the account setup window. Then, switch back to online status and see if the account works. Incoming IMAP server: imap.1and1.com on port 993, SSL/TLS, normal password, email address for User name. Outgoing: smtp.1and1.com on port 587, STARTTLS, normal password, email address for User name.

To clarify password vs other issues, I recommend setting account up but without password. That generally lets you know if thunderbird has the correct settings. I would delete the account and then go to settings>Privacy&security to verify that the account isn't present and also to check help>troubleshootinginformation to verify that the Mail & News Account table doesn't show it. Then set up without password and wait for a prompt for it after setup. That may not make the account work, but may help. I've never see the message you posted before, and wish I had more substantive advice.