Some of this is forwarded mail, not an attack
NOTEWhat it means
N messages (N%) show the signature of relayed mail, a mailing list or an auto-forward that changed the envelope on the way. It is normal, it is not someone impersonating you, and it is the single most common reason a healthy domain sees failures.
How to fix it
Leave it alone. Just make sure those messages are DKIM-signed, because a surviving signature is what keeps forwarded mail passing DMARC.
Check your own domain
This page describes the condition. To find out whether your domain has it, run the RUA test or the full checkup, which examines every record at once.
Understand it properly
This page covers one condition. For the whole picture, The DMARC guide, including how reporting works, or start at the Health Library.
Where this comes from
We judge this against RFC 9990 section 3.1.6. Every finding on this site cites the specification behind it so you can check the work rather than take our word for it.
Other RUA conditions
RUA_FORWARDED_MAIL
Every fix on this site is yours to implement. If you would rather someone did it, I take this work directly.