Since late last week, Outlook.com and Microsoft’s other consumer mail services have been rejecting legitimate mail, reports The Register. Senders get non-delivery reports pointing at SPF validation failures or missing DMARC records.
It looks like Microsoft tightened its accept rules. Its 2025 bulk-sender requirements (SPF, DKIM and DMARC for domains sending 5,000+ messages a day) now seem to be hitting small senders too, sometimes on a single one-line email.
My take
Garlic, because rejecting a one-liner from a small domain is a half-baked rollout. But the fix on our side is easy and overdue: publish a valid SPF record, sign with DKIM and add at least a p=none DMARC record. I wrote up how to check all three with dig.
God Bless, and Needs Garlic!
