Your DKIM signatures are being broken on the way

What it means

N sources show a signature from your own domain that failed verification on relayed mail. Something between you and the recipient is editing messages, a mailing list footer, a subject-line tag, or a gateway rewriting the body, and that edit invalidates the signature.

How to fix it

Sign with relaxed/relaxed canonicalisation so light reformatting survives, and keep signed header lists short. Mailing lists that rewrite the From address will always break DKIM, and ARC is the only real answer there.

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 9989 section 4.4.1. Every finding on this site cites the specification behind it so you can check the work rather than take our word for it.

Other RUA conditions

• You are ready to turn enforcement on
• Some of this is forwarded mail, not an attack
• Somebody is sending as you, and it is being delivered
• Unauthenticated mail is getting past your policy
• Your policy stopped forged mail
• Your own mail is failing authentication