Reason
The Forward-confirmed reverse DNS (FCrDNS) check has failed:
None of the PTR RR domains of your mail server IP address resolve in the Domain Name System (DNS) to an IP address that corresponds to the IP address of your email server.
Solution
Please correct your DNS records so that the name resolution of your PTR-RR domain(s) returns also the IP address that is assigned to your email server.
Further information on Forward-confirmed reverse DNS (FCrDNS) can be found here. DNS setup recommendations can be found in RFC 1912.
As soon as your adjustments have been published in the DNS and the check is successful, you can successfully deliver emails to us again.
See also: General information on our error messages.