I wanted to move a lot of folders I have in Thunderbird stored locally.

My goal was to put them in one of my webmail accounts.

But I kept getting into trouble, and was only able to move about half of my folders.

I investigated size and other thing I could find on the web, but with no succes.

But finally I got to the solution. One of my foldes was named with a »dot« in it. After renaming this folder, I had no more problems.