I have found the problem, It was my fault, I was trying to forward emails on an ISP that was not allowed, a bit like posting main though NZ Post and trying to use an ABC Post, postage stamp.
Thanks for your comments and help, CR4 contributers.
This forum page should provide your answer. If not, please include which version of Thunderbird you are using. Since this forum is focused on your problem, I hope the only reply will be success!