Piggynose:
What I'm saying is that the first thing you need to do is to get yourself a GMX account, totally separate to anything to do with any existing accounts which you may have. (Choose a totally new account name, such as '
[email protected]' and a new password, such as 'oink123oink')
Then you can log into that account and set up the 'Mail Collector' facility to divert mail from your 'old' account(s) into your GMX one. (You can choose whether such mail goes straight into your GMX inbox or to a separate folder dedicated to mail from your old account. You can also choose whether to leave a copies of diverted emails at your old email facility or have them automatically deleted from there).
It's still unclear to me as to whether:
(a) you've set up a new GMX account;
(b) you've then tried to configure the 'Mail Collector' facility ; and, if so,
(c) what error message you're actually seeing.