I couldn't send email, so I deleted and re-setup my email account. This lost my remembered passwords, so now I can neither receive or send email. My basic password still lets me onto TB though. I have the password to log on to TB, and I know another password that was working for something when TB was working before the upgrade, although this password is not now working for any of the servers.

By 'basic password', are you referring to Primary Password?

it's the password that gets me onto TB.

That would be the Primary Password. If the account passwords are not remembered, you will need to contact the email provider.

I logged onto my Spectrum account after changing my password. After that, everything in TB worked. It now requires a password to run TB, a password to get messages, and a password to send messages. I'm getting passworded to death. But I'm happy that TB is working again (after the update).

The password to run TB is optional and can be stopped, if desired, at 'settings>privacy&security' - UNtick 'use primary password'