When Microsoft sets the email rules

 

This month, on May 5th, Microsoft introduced stricter authentication requirements for email senders.

These changes affect anyone sending more than 5,000 emails per day to recipients at Outlook.com, Hotmail, or Live.com — including email marketers, bulk senders, and automated announcement systems.

Even if you send on behalf of clients (as an ESP or platform provider), you are considered the sender unless the messages are authenticated using the client’s domain with proper SPF, DKIM, and DMARC alignment.

What’s Required to Stay Compliant:

• ✅ SPF: Make sure your domain has a valid SPF record, and it passes validation.
• ✅ DKIM: Sign your messages with DKIM to prove they haven’t been tampered with.
• ✅ DMARC: Publish a DMARC policy (at least p=none) that aligns with SPF or DKIM.
• ✅ Avoid noreply@ addresses: The “From” and “Reply-To” addresses must be valid and capable of receiving replies.
• ✅ Include a one-click unsubscribe link: Make it easy for users to opt out.

Why It Matters:

Failure to comply means your emails may be rejected outright, never reaching your audience. This can seriously impact your engagement, deliverability, and reputation.

By meeting these new standards, you not only avoid Microsoft’s filters, but also improve your overall sender reputation and email performance.