::T-Online ::POLIfórum

IP address to check

The reverse name of your IP address does not map back to the same IP

EXPLANATION:

We try to resolve the reverse name (PTR) of the sending machine's IP address and then try to resolve that name back to it's IP address.
These two must exist and be the same. You get this error if they weren't, or they did not exist in the DNS, when we tried to resolve them.

SOLUTION:

It seems that the IP address of your mail relay does not have a reverse name in the DNS, or the reverse name for your IP is not resolveable to the same IP.
Please ask your service provider to correctly set up the DNS for the IP address.