New requirements for bulk senders in Outlook: what you need to know

 

🚨 What will change?

If your organization sends a lot of emails to Outlook.com, Hotmail or other Microsoft email users, you need to comply with these new technical requirements:

• ✅ Authentication required:
  Emails must be authenticated via SPF, DKIM and DMARC. This verifies that emails really come from your domain.

• 🚪 Easy unsubscribe:
  Every bulk email should provide a simple “unsubscribe” option directly in the email header. Users should be able to unsubscribe with a single click. 📤

• 📉 Spam rate below 0.3%:
  If more than 0.3% of your emails are marked as spam, Microsoft may start blocking your emails. Time to send really valuable content! 😉

 

🛡️ Why is Microsoft doing this?

These measures are designed to:

• 📭 Increase the reliability of email communications

• 🎯 Better protect users from phishing and spoofing

• 🧹 Reduce the amount of unwanted emails

The goal is clear: a cleaner and safer inbox for everyone.

 

🧰 What should you do as an organization?

For many companies – especially marketing and sales-oriented organizations – this means that the technical setup of email needs to be in good order. Make sure you:

• 🔍 Checking your DNS settings for SPF, DKIM and DMARC

• 🛠️ Adapting your email platforms to meet the new unsubscribe requirements

• 📊 Monitor your spam complaints via Microsoft’s reporting or feedback loops

 

📅 When does this go into effect?

The new requirements will become active as of May 5, 2025. Organizations will have until then to adjust their systems. Microsoft will enforce more strictly starting that month.

 

Frequently Asked Questions

❓ Why does Outlook mandate this for bulk senders?
Because large senders (>5,000 mails/day) are more at risk. This significantly reduces the chance of spam & spoofing.

❓ How do SPF, DKIM and DMARC benefit me?
They improve your deliverability, strengthen your brand and reduce bouncebacks. Win-win in other words! 💡

❓ Should I do this at < 5,000 mails/day?
Yes! Authentication is best practice for any sender. It protects your reputation and increases your reliability. ✔️

❓ Does the Safe Senders List help bypass rules?
No. Outlook ignores the Safe Sender List in this new enforcement. Rules apply to everyone. 🚫📬

 

 

💡 Tip from ALTA-ICT

Want to make sure your e-mail traffic is compliant with the new rules? Have your email environment vetted by an expert. At ALTA-ICT we are happy to help you with:

• Implementation of SPF, DKIM & DMARC

• Analysis of your opt-out structure

• Advice on email deliverability & security

Contact us at alta-ict.co.uk/contact! 📩

 

References

¹https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730

 

About the author

My name is Alta Martes, a specialist in Microsoft 365 and Google Workspace, with a focus on modern workplace management, cloud security and identity & access management. With years of experience, I help organizations optimize their IT infrastructure and create a secure, efficient digital workplace.

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