Microsoft Strengthens Outlook’s Email Ecosystem to Protect Inboxes

Microsoft will enforce stricter email authentication for high-volume Outlook senders (5,000+ emails/day) starting May 5, 2025, requiring SPF, DKIM, and DMARC (at least p=none), with non-compliant messages routed to junk and potential future rejections. The guidance also emphasizes valid sender addresses, functional unsubscribe links, list hygiene, and transparent mailing practices to enhance deliverability and reduce spoofing and phishing.