Set up DMARC for Your Domain

DMARC tells receivers how to handle unauthenticated mail.

Recommended start

_dmarc.example.com TXT: v=DMARC1; p=none; rua=mailto:dmarc@example.com; pct=100; adkim=s; aspf=s

After monitoring, move to p=quarantine and then p=reject as alignment improves.