Email continues to be one of the most widely used tools, both personally and professionally. It's fast, direct and effective for connecting with customers, sharing information and maintaining an active relationship with your audience. But that same popularity also makes it an easy target for abuses such as spam, phishing and phishing.
To address this situation and protect millions of users and small businesses, Outlook is raising the bar on security and best practices. Microsoft has announced new mandatory requirements for those sending more than 5,000 emails per day, including the proper configuration of key protocols such as SPF, DKIM and DMARC. The goal is clear: to strengthen email authentication, reduce malicious content and improve the deliverability of legitimate senders.
This move not only seeks to shield inboxes, but also to drive positive change across the entire email marketing ecosystem. If your company works with mass mailings, newsletters or automated communications, it's time to get ready. It's not just about compliance; it's about protecting your brand, improving your bottom line and being part of a more trusted digital environment.
New Outlook 2025 Requirements
If your domain sends more than 5,000 emails a day, there are new rules on the way that you can't ignore. Outlook will start requiring you to have three key things configured correctly: SPF, DKIM and DMARC. If you don't comply, your emails will start to fall into the spam folder, and if the problem continues, they could be blocked outright. This is what you will need to have in order:
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SPF (Sender Policy Framework): This record in your DNS must clearly state which servers are authorized to send emails on behalf of your domain. If someone tries to send from an unlisted server, the system detects it and marks it as suspicious.
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DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to your emails so that it can be verified that the content was not altered and that you really sent it. It is a way to validate the integrity of the message.
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DMARC (Domain-based Message Authentication, Reporting and Conformance): This is like the conductor. It tells the destination servers what to do if the message does not pass SPF or DKIM. The minimum you will need is a “p=none” policy (to receive reports), and that the domain is aligned with SPF or DKIM (ideally both).
Extra recommendations to keep your mail clean and reliable
If you are one of those who send a lot of emails a day, there are some good practices that are worth following to maintain a good reputation and avoid headaches:
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Use valid and reliable addresses in the “From” or “Reply To” field: make sure these addresses really exist, represent your domain and can receive replies. Nothing generates more distrust than an email that cannot be responded to.
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Include clear unsubscribe links: Your recipients should be able to easily stop receiving your emails if they want to. This is especially important in marketing campaigns or mass mailings. And yes, the link must work.
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Keep your list clean and up to date: Periodically delete addresses that bounce or no longer exist. This helps you reduce spam complaints and improves deliverability.
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Be transparent with what you send: Use clear subject lines and avoid misleading tricks. Also, make sure that the people you are writing to have given you permission to do so. Trust is earned, not assumed.
Important: Outlook can take measures such as filtering or even blocking your emails if it detects serious authentication problems or bad practices in the management of your lists.
And when does all this come into play?
You'll want to get up to speed now. Microsoft recommends that all senders (and especially those handling large volumes) review and update their SPF, DKIM and DMARC settings as soon as possible.
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As of May 5, 2025, mails that do not comply with these rules will start going straight to the spam box. This will be a kind of “warning phase” so that you can correct what is necessary without more serious consequences.
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Later on (no exact date yet), emails that still do not comply could be completely rejected to protect users. So you'd better be ready before then.
Next steps (what you can do from today)
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Do a complete review of your DNS records: Verify that you have SPF, DKIM and DMARC configured correctly. If you don't know where to start, here you can see the authentication headers and learn how to read them.
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Stay tuned for updates: Microsoft will be releasing more information about the exact dates when the final rejections will start to be applied. You will want to keep an eye on the official blog.
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Join the change: Improving authentication and taking care of the hygiene of your emails not only helps you to get them to the inbox, you are also doing your bit to ensure that email remains a secure and reliable channel for everyone.
Frequently Asked Questions (FAQ)
Why is Outlook requiring these changes to those who send a lot of emails?
Because those who send large volumes of emails (more than 5,000 per day) are more likely to affect the security of inboxes. By targeting this group, Microsoft seeks to stop spam or spoofing campaigns before they reach users.
How do SPF, DKIM and DMARC help me as a sender?
Basically, these protocols work as an “identity verification” for your emails. If they are properly configured, your recipients' servers will know that your messages are legitimate. The result? Better deliverability, fewer bounces and more trust in your brand.
What if I send less than 5,000 emails a day, do I have to worry about that too?
It's not mandatory yet, but highly recommended. Having SPF, DKIM and DMARC properly configured helps protect your sender reputation from now on. Better to be safe than sorry.
What is a “functional” unsubscribe link?
It is a button or link within the email that allows the person to stop receiving messages from you with a single click. It has to be well visible and work properly. If you hide it or it doesn't work, you could get in trouble.
Is this going to eliminate all spam?
Hopefully, but no. No system is perfect, but these measures make things much more complicated for those who cheat and improve the experience for those who do get things right.
What does “alignment” mean in DMARC?
Alignment means that the domain that appears in the “From” field must match the one you use in SPF or DKIM. This prevents someone else from using your domain name to send fake emails.