Email address rejected, cannot add him to club FTH website

The club is in the US and the member is in Germany and has gmx.net domain. I can't even add his information in the Membership list.

At first he was not getting the emails, now they are totally rejected. Error message says

Invalid/Non-functioning E-mail: (user name)@gmx.net (No advertised SMTP servers are accepting mail.)

Let me know if you want me to send his actual email address, didn't want to post on a public forum.

Your help is appreciated.

I will need the exact email address you are trying to use.
And your club number or we ca do nothing for you.

Sent via direct private message to you.

fixed and added