Gmx.de access was already fixed in a previous Beta and now @Web.de account access is fixed too.
You can request Beta access here
gmx.net never works. I can't create one email account with them that stays functional. Re-logging in never works.
I created an email account with their sister site, web.de, but now that wont work unless I upgrade my browser to their partner's browsers... the latest data stealing versions of Firefox and Internet Explorer!