SPF authorises a private or reserved IP
NOTEWhat it means
the offending value is an address that never appears on the public internet, so it can never match a real delivery. It is wasted space in the record, usually left over from an internal test.
How to fix it
Remove the offending value, or replace it with the public address your mail actually leaves from.
Check your own domain
This page describes the condition. To find out whether your domain has it, run the SPF test or the full checkup, which examines every record at once.
Understand it properly
This page covers one condition. For the whole picture, What is SPF, and the ten-lookup limit, or start at the Health Library.
Where this comes from
We judge this against RFC 7208 section 5.6. Every finding on this site cites the specification behind it so you can check the work rather than take our word for it.
Other SPF conditions
SPF_PRIVATE_IP_IN_SPF
Every fix on this site is yours to implement. If you would rather someone did it, I take this work directly.