Following the lead of Gmail and Yahoo, Microsoft is raising the bar for bulk senders to improve inbox experiences across Outlook and other services. This will impact senders delivering over 5,000 messages per day to Microsoft domains, including Outlook.com, Hotmail, Live, or MSN. Failing to comply with the new requirements could result in your messages being throttled, sent to junk, or rejected.

Steps to take to meet Microsoft’s authentication standards

 

According to Microsoft, “these measures will help reduce spoofing, phishing, and spam activity, empowering legitimate senders with stronger brand protection and better deliverability." 

To stay ahead of the game, make sure that you meet these email authentication-related requirements:

• All high-volume senders must have SPF, DKIM, and DMARC properly configured

• Microsoft’s DMARC recommendation is to publish a DMARC record with a policy minimum of p=none, to begin monitoring, and plan for enforcement (quarantine or reject)

• Messages must have alignment, meaning that one or both (preferably) of the SPF or DKIM authentication domains must match the from domain

Note: if you’re already compliant with the Gmail/Yahoo authentication standards, you should not have anything to do.

Senders should also adopt Microsoft’s best practices to maintain “quality and trust”

 

Complying with these authentication standards is just one of the measures Microsoft is enforcing. They are also pushing the broader industry toward more transparency to build trust, drive engagement, and help protect recipients.

While we know the tips to increase email deliverability, Microsoft mandates large senders to practice the following:

• Provide an easy, clearly visible way for recipients to opt out of further messages, particularly for marketing or bulk mail 
• Keep your list clean and remove invalid addresses regularly to reduce bounces 
• Bouncing addresses should be processed and suppressed 
• Use accurate subject lines, avoid deceptive headers, and ensure your recipients have consented to receive your messages to avoid spam complaints and ensure high engagement with your campaigns

Note: while enforcement first targets large senders, we strongly recommend all senders to follow these best practices and adopt strong authentication.

Start preparing ahead of the enforcement timeline

 

According to Microsoft’s announcement, “after May 5th, 2025, Outlook will begin routing messages from high volume non‐compliant domains to the Junk folder, giving senders an opportunity to address any outstanding issues.”  

We expect full rejections for senders who don't follow these guidelines. With these changes taking effect in May, preparation should start now. Our deliverability experts from the professional services team can help you make necessary changes through our deliverability offering, which covers everything from authentication checks to DMARC policy enforcement, bounce and abuse complaints monitoring, email hygiene recommendations, and quick wins that can ensure good email deliverability.

Setting new standards for the future

 

While Gmail and Yahoo enforced these requirements last year, Microsoft’s adoption signals a permanent shift across all major providers. Now, the top four inbox providers (Google, Yahoo, Apple, Microsoft) are aligned on requiring authentication, consent, and good list hygiene.  

Marketers who prioritize healthy mailing practices, transparency, trust and monitor deliverability closely will come out ahead. Reach out to our team if you have any questions or need help meeting these requirements.