A colleague of mine pointed out last night that Outlook.com changed its DNS record from publishing no DMARC policy to publishing a record specifying “p=none; pct=100”.
In DMARC, “p=none” is used to collect feedback and gain visibility into email streams without impacting existing flows.
Earlier this spring, both Aol and Yahoo began publishing “p=reject; pct=100” on some or all of their domains’ DMARC records, causing lots of mail to be rejected at all domains that participate in DMARC – and not just spam. The change caused mail lists to break and inflicted serious deliverability damage on small businesses who’ve relied on Aol or Yahoo for their business needs for years.
Outlook.com hasn’t made any public announcements about when or if they will publish a reject record, but I take yesterday’s change as a clear sign that they’re thinking about it.