I can't get GMail in GMX - I get an email from GMail telling me that an insecure device using outdated security settings has tried to access my account.
Do you get the same?
You need to verify that you give permission for the GMX Mail collector program to access Gmail.
•First, sign into the Gmail account you want to collect mail FROM
•Then go here: https://accounts.google.com/b/0/DisplayUnlockCaptcha
Then go back to your GMX account and try setting up Mail Collector again.