I enter my e-mail address and everything else works out fine, until i try to sign up and it says my e-mail-adress (which is then same one i am using for this account btw) is invalid. I triple-checked to see if I spelled it right, but it still won’t take it, even though it is a completely standard GMX-e-mail-adress 
Error code: 76782
Just 2 questions; what’s your MSN Messenger version and have you tried through Escargot Web?
Correct me if I’m wrong, but I don’t think that either of these things matter in this situation, because the problem lies in creating the account.
Edit: I think i have discovered the problem, escargot simply doesn’t support GMX. What an unecessary flaw.
That error code does not exist. GMX emails are supported.
I had replied with something else but I have decided to have a GMX (just for a test) to create an account on MSN but I got the same error (a 0 is missing from the issue post): 767820