In my experience, people who are interested in adding a DMARC record for their domain start with setting one up with p=none. Then they go through and audit the reports on their domain. They see that we are sending email with unmunged From lines, and contact us asking us to fix our problem. This happened twice this past week and has happened on a somewhat regular basis over the past year or two.

That said, I've rolled back the DMARC change that I had pushed earlier today; we are once again not re-writing From lines for p=none.

Thanks,

Mark