Microsoft Cracks Down on Bulk Email: SPF, DKIM, and DMARC are Now Mandatory
2025-05-05
Microsoft is now strictly enforcing new email authentication rules. Senders exceeding 5,000 messages daily to Outlook.com (including hotmail.com and live.com) must be properly configured with SPF, DKIM, and DMARC to ensure deliverability. Failing to meet these requirements will result in emails being bounced, not just relegated to spam. This crackdown targets spam, spoofing, and phishing, but will impact marketers and businesses relying on mass email. Even legitimate emails risk being blocked without proper authentication. Companies must ensure their SPF records, DKIM signatures, and DMARC policies are correctly configured and regularly review mailing lists and unsubscribe links.