Reverse DNS does not confirm forward
ATTENTIONWhat it means
the offending value has a PTR pointing at example.net, but that hostname does not resolve back to the same address. Strict receivers treat a reverse record that does not round-trip as no reverse record at all.
How to fix it
Make them agree: the PTR names a host, and that host needs an A or AAAA record pointing back to the offending value.
Check your own domain
This page describes the condition. To find out whether your domain has it, run the PTR test or the full checkup, which examines every record at once.
Understand it properly
This page covers one condition. For the whole picture, Why mail lands in spam, in the order worth checking, or start at the Health Library.
Where this comes from
We judge this against RFC 1912 section 2.1. Every finding on this site cites the specification behind it so you can check the work rather than take our word for it.
Other PTR conditions
FCRDNS_FAIL
Every fix on this site is yours to implement. If you would rather someone did it, I take this work directly.