Thunderbird Password Problem

I live in Germany and use Deutsche Telekom's T-Online system for my main e-mail system, so my email address is: k.vanleuven@t-online.de Due to some security problem, I had the change my T-Online e-mail password and since this time I can't send or receive e-mails from my German version of Thunderbird. Thunderbird asks me for the"secureimap.t-online.de" server password, but it doesn't recognize the new password that I have for my T-Online e-mail system. I store my e-mails in various folders folders in Thunderbird and I want to continue using Thunderbird for my e-mail management. I think I might have to re-install Thunderbird from scratch. Must I do this, if so haw do I save all my e-maile files? Your help in solving this problem will be very much appreciated. Karl Van Leuven