How to Move a Domain from p=none to p=reject Safely — A Practical Guide

Changing your DMARC policy sounds simple in theory. Flip p=none to p=reject, sleep better at night. In practice, organizations that rush that change often spend the next day undoing it after legitimate email stops arriving.

The admins who do this successfully treat the migration as a monitoring exercise first. They spend weeks or months reading their aggregate reports, identifying every legitimate sender, and only then tightening policy - in stages. Here's the model that actually works.