I've had a GMX account for many years and it is a decent service, but they do want a RL name and address, which they don't verify but check for plausibility, e.g. I had to give a street name with the right postal code (at least they do that for German customers, no idea about international). Also for a free account they want information of your demographics, education, income, interests etc so they can send you a targeted advertising newsletter. Obviously you can make up anything and filter their stupid advertising into your spam filter (which I do), but they regularly nag you to control and update your information (every six months or so) in one of their forms.