SPF redirect points back into its own chain
CODE REDWhat it means
The redirect chain a.example.com to b.example.com returns to a domain it already passed through. Evaluation cannot terminate, so receivers return a permanent error.
How to fix it
Break the loop, one of the domains in that chain should hold the real policy, and the others should point to it or list senders directly.
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 6.1. Every finding on this site cites the specification behind it so you can check the work rather than take our word for it.
Other SPF conditions
SPF_REDIRECT_LOOP
Every fix on this site is yours to implement. If you would rather someone did it, I take this work directly.