GMX does not accept

GMX does not accept

Since this week the German mail provider GMX does not accept any of my mails. Please help!


This is the mailer daemon response:

THIS IS A WARNING MESSAGE ONLY.

YOU DO NOT NEED TO RESEND YOUR MESSAGE.

The original message was received at Sun, 28 Aug 2016 10:45:45 -0700
from g.schmidt@zoho.com [ g.schmidt@zoho.com]

----- The following addresses had fatal errors -----
[Status: Error, Address: < xxxxxxxxxx@gmx.de>, ResponseCode 421, gmx.net (mxgmx101) Nemesis ESMTP Service not available
Service unavailable
Reject due to policy violations.
For explanation visit http://postmaster.gmx.com/en/error-messages?ip=74.201.84.153&c=poli, Status: Error, Address: < hxxxxxx@gmx.de>, ResponseCode 421, gmx.net (mxgmx011) Nemesis ESMTP Service not available
Service unavailable
Reject due to policy violations.
For explanation visit http://postmaster.gmx.com/en/error-messages?ip=74.201.84.153&c=poli]