Microsoft Outlook is introducing new rules which will impact high-volume senders.
The changes were quietly announced in a blog post on Microsoft’s website, meaning many affected senders could be unaware of the changes they need to make.
Unaware of the upcoming rule changes to Outlook? If you use Outlook to send large numbers of emails, you may need to take manual actions today to avoid various penalties being applied to your email domain.
EcoSend is here to give you the lowdown on what to do next.
What Are The Outlook Changes For Senders?
Similar to changes introduced by Gmail and Yahoo back in 2024 aimed at tackling email spam, Microsoft Outlook has followed suit by stepping up its sender requirements for high-volume senders. It applies to those who send at least 5,000 emails per day.
In a bid to “preserve trust in the digital ecosystem”, Microsoft Outlook requires senders to comply with the following from now on:
✅ DKIM (DomainKeys Identified Mail) - DKIM is a way to authenticate emails and prevent email spoofing. Another way of describing DKIM is by using a digital signature, which enables your recipients' server to authenticate your email campaigns.
✅ DMARC (Domain-based Message Authentication, Reporting and Conformance) - Controls what happens when authentication fails. Microsoft Outlook requires senders to “have least p=none” which is a term that relates to their policy settings of DMARC.
✅ SPF (Sender Policy Framework) - No, your emails will not need sunscreen. But they will need the other type of SPF, which ensures servers are enabled to send emails out with your domain credential.
Psst: New to these email authentication protocols? Learn more about DKIM, DMARC & SPF with our free guide!
Microsoft Is Also Recommending That Senders Maintain Good List Hygiene
Beyond ensuring your emails have DKIM, DMARC and SPF enabled, Microsoft Outlook also wants senders to look at other aspects to avoid emails ending up in the spam folder.
These include:
Compliant sender information (i.e. use real sender names and addresses)
Remove invalid or inactive email addresses regularly
Provide visible one-click unsubscribe links
Use transparent email practices (i.e. accurate subject lines)
Only send emails to those who have consented
Similar to the Gmail and Yahoo sender changes, maintaining a clean email list by only emailing those who have consented to hear from you, plus removing inactive contacts offers many benefits for senders.
In short, these measures look to boost open rates, engagement rates and conversions.
When Will The Changes Happen? 📆
Microsoft Outlook will begin rolling out the changes on May 5th, 2025. Users who send 5,000 emails per day via Outlook will need to comply before then.
If you are reading this post after the above date, it is important to check you are fully compliant with the requirements. That’s because the changes will apply to all senders from now on.
What If I Don’t Comply?
Microsoft Outlook is serious about its new sender requirements, stating that high-volume senders who don’t comply will face a series of “negative actions.”
The penalties include filtering messages so that they go straight to the spam or junk folders of your recipients.
For the most serious breaches, including having poor list hygiene, Microsoft states it may even block accounts from being able to send emails altogether.
I’m Not An Outlook User - Should I Still Step Up My Sender Compliance?
Yes! As noted above, Gmail and Yahoo which are two of the biggest email clients have already made changes to reduce spam on their platforms. Many of these new requirements overlap with Microsoft Outlook’s new sender rules for 2025.
Overall, it’s essential that your emails appear genuine to email servers and users alike email sender (regardless of the platform you use). Otherwise, your emails are more likely to end up in the spam folder which will also harm your email ROI.
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