GMX is a very poor e-mail service. Stay away from it! It is used for frauds and the company does nothing to stop it.
Criminals use my e-mail adress as contact adress over and over again when they register a new GMX e-mail adress. I have several times demanded that this bad company block people for using my e-mail adress as contact adress. It easy to do but this lazy company does nothing. Don't use GMX mail if you want to stay out of trouble.