Because i searched for any import solution to import other accounts from thunderbird.
I saw that this allready was requested back in 2006 and is still not available, as it is on many other free mail clients.
Well, it looked good, but since you have to do many many things to get your accounts in here, i can spend my time better.
On other clients there is just a button when installing the client to import accounts from several other clients.
That is a missed change.
Yes even typing this message is quicker then importing any account from thunderbird.
So i am going to look further for a good replacement.