SPF includes itself in a loop
CODE REDWhat it means
The include chain a.example.com to b.example.com comes back to where it started. Evaluation burns lookups until it hits the limit and returns a permanent error.
How to fix it
Break the loop, remove the include that points back up the chain, and list that sender’s IP ranges directly if it is still needed.
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 5.2. 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_CIRCULAR_INCLUDE
Every fix on this site is yours to implement. If you would rather someone did it, I take this work directly.