Microsoft’s New Email Authentication Rules (May 2025): What it Mean for You?

As we enter 2024, Gmail and Yahoo announced new rules which required bulk senders to implement strict authentication methods, like SPF, DKIM, and DMARC, along with a clearly visible one-click unsubscribe option, improving their platforms’ security and improving marketers’ practices.

Now Microsoft is planning to do the same. Effective May 5, 2025, Microsoft is changing requirements for all bulk email senders to any email targeting Outlook, Hotmail, Live.com, and other Microsoft domains.

In simple terms, if you send more than 5,000 emails a day, your emails must be authenticated using SPF, DKIM, and DMARC. Currently, Microsoft is only indicating it will mark emails that aren’t authenticated as spam, but ultimately will get to a point where those emails are blocked.

This article will explain Microsoft’s new requirements, compared to what Gmail and Yahoo have provided, and how email marketing providers such as Moosend and GetResponse are providing an easy way for users to comply with the requirements.

Why Microsoft’s New Rules Matter?

The changes Microsoft is making to its authentication requirements for bulk email senders are a watershed moment for the evolution of email’s security and marketing landscape.

With cyberattacks and phishing attempts taking on more sophisticated methods with reckless abandon, email service providers (ESPs) are feeling added strain to protect users from malicious actors.

Microsoft happens to carry millions of users on Outlook.com, Hotmail.com, and Live.com, and by making these proactive changes, Microsoft is attempting to be sure that legitimate emails land in their users’ inboxes.

Also Read: How to Encrypt the Emails in Microsoft Outlook and Office 365?

The change Microsoft is requiring is that bulk senders (anyone sending more than 5,000 emails a day to Microsoft domains) use three technology protocols–SPF (Sender Policy Framework), DKIM (Domain Keys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance).

These protocols all work to verify a sender’s identity to curb email spoofing and abuse of bulk email to mitigate spam.

How to Meet Microsoft’s Email Standards?

SPF (Sender Policy Framework):

SPF is the basis of email authentication. SPF allows domain owners to specify which IP address(es) can send email on their behalf.

So when an email is received, the recipient’s email server references an SPF record, published in the domain’s DNS (Domain Name System), that tells the email server whether the sending server is allowed to send on behalf of that domain.

If the sending server isn’t listed in the SPF record, there is a possibility the email will be flagged as suspicious, or in some cases automatically rejected.

One of Microsoft’s new email authentication requirements specifies that senders MUST have a valid SPF record that not only exists, but passes the verification check.

This is a critical step to prevent domain spoofing, which is a common method used by attackers to send email by pretending to be sending from a domain the receiver trusts.

Marketers should be aware that it’s very important to have a properly maintained SPF record to improve deliverability and help protect their brand from being spoofed.

DKIM (DomainKeys Identified Mail)

DKIM improves authentication further by incorporating a digital signature onto the message as it leaves your organization’s environment.

The signature is created with a private key and can be verified by the recipient’s server with a public key that was published in the DNS.

The DKIM signature will fail if the message content or headers are modified while in transit, indicating that the message may have been modified in some other way.

Microsoft’s updated policy introduced the mandate that DKIM needs to be not only set up, but also pass the verification check.

For legitimate senders, DKIM provides a means of proving that the email was sent from a legitimate server and verifying that the message was not modified while in transit.

This gives inbox providers and email recipients an added level of trust, which statistically increases the likelihood of placement into the primary inbox, rather than the spam folder.

DMARC (Domain-based Message Authentication, Reporting, and Conformance)

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a domain-wide policy that ties SPF and DKIM together.

It enables domain owners to state how they want the receiving mail servers to deal with messages that fail SPF or DKIM, for example, by requiring receivers to quarantine or reject those messages and to inform them regarding any emails sent on their behalf.

Also Read: Importance and Benefits of DMARC, BIMI and VMC Certificates for Businesses

Recently, Microsoft now also requires there to be a DMARC record with at least a “p=none” policy, meaning there are no enforcement mechanisms in place, but they are monitoring the information about it.

Senders should ultimately target order policies of “p=quarantine” or “p=reject” for maximum security.

Ultimately, DMARC provides much better visibility into their email ecosystem for senders and allows senders to discover abuse or unauthorized use of their domain more easily and manufacturers cannot effectively impersonate mail senders and poorly constructed emails.

Aligning Your Sending Domains

DMARC alignment requires that your SPF and/or DKIM domains align with the domain in the “From” address of your emails, preventing spoofing once you authenticate that emails are coming from a verified and expected sender.

If it doesn’t align, even if SPF or DKIM passes, DMARC will fail, and deliverability issues will happen. Make sure to check all domains from which you’re sending emails, especially with third parties.

You will need to adjust your DNS records and email settings for your marketing templates, transactional email providers, and CRMs so that ALL of them authenticate using the same domain on your “From” header.

This is necessary to validate the DMARC settings by Microsoft and to maintain inbox placement.

Utilize a legitimate “From” and “Reply-To” address

Microsoft recommends — and many mailbox providers expect — a real and working “From” or “Reply-To” address. This helps customers trust the sender and can help reduce Spam complaints.

Do not use generic email addresses that include “noreply@” or random numbers/letters and combinations. Use professional, human-addresses that clearly define who you are (ie..your brand or support team) to your customers.

A working address is critical when receiving replies from customers so you can respond (especially for transactional or service purposes). Test out your “From” and “Reply-To” addresses to ensure they are working and monitored.

Try not to change your email addresses frequently as it can create problems with spam filters and your audience may feel confused.

Include a Clear Unsubscribe Link

Although Microsoft doesn’t enforce it specifically, it would be very helpful to include an easily visible and clickable unsubscribe link which would make it easy for the recipients to unsubscribe if they don’t want to receive any information anymore.

It’s important to submit to spam complaints too since spam complaints negatively impact uw contacts and reputation which surely will affect your ability to deliver messages.

If you do have this functional link, try to include it at the bottom of your emails and in readable font and plain language. Most autoresponders like GetResponse typically place the compliant unsubscribe link on every email template.

Always honor opt-out requests as soon as possible so that you remain compliant with your respective anti-spam laws and not violate traditional best practices.

Clean Your Email Lists Regularly

One recommendation Microsoft advocates for senders is to practice regular list hygiene. Whether over time or due to consumer fatigue, email lists will develop invalid or inactive emails which will either generate hard bounces or leave the recipient disengaged.

You can clean your lists by removing email addresses that are not engaging with your emails for months and email addresses that have unsubscribed or bounced. A proactive approach is to use double opt-in mailing list forms to acquire high-quality subscribers.

Cleaning your email list regularly will help reduce spam complaints, improve open rates, and maintain your sending reputation.

Most email service providers will have built-in tools that can automatically identify and filter out inactive users from your lists to help maintain healthy and deliverable lists of email recipients.

Use Accurate Subject Lines and Headers

The third email sender guideline from Microsoft is that misleading subject lines or header information is unethical and against worldwide anti-spam laws.

As a sender of an email campaign, your subject line should convey the true nature of the content of an email message.

Do not engage in clickbait tactics that may keep one part of an email out of the spam category but still may result in offense to the recipient and could lead to spam complaints.

Along the same lines your headers — including the “From” name and address — should accurately inform recipients of the sender.

Both metadata elements foster sender-trust by the recipient and provide trust in sender-to-email provider as well — Microsoft not excluded.

It is worth mentioning that Microsoft utilizes algorithms to assess both content and metadata to evaluate sender reputation, and believe it or not, being credible yields trustworthy subject lines and identities that recipients will enjoy and look for in their inboxes and email campaigns to get placed consistently into the inbox.

Microsoft vs Gmail and Yahoo Email Sender Requirments

Feature/Requirement	Microsoft (May 2025)	Gmail & Yahoo (Feb 2024)
Applies To	Senders sending 5,000+ emails/day to Outlook, Hotmail, Live.com	Senders sending 5,000+ emails/day to Gmail and Yahoo addresses
SPF Required	Yes, must pass	Yes, must pass
DKIM Required	Yes, must pass	Yes, must pass
DMARC Required	Yes, at least p=none policy	Yes, at least p=none policy
DMARC Alignment	Required (SPF or DKIM must align with From domain)	Required (SPF or DKIM must align with From domain)
Unsubscribe Link	Strongly recommended in marketing emails	Required via “List-Unsubscribe” header & visible in email
Spam Threshold / Complaint Rate	Not explicitly mentioned	Must keep spam complaint rate under 0.3%
Enforcement Start Date	May 5, 2025	February 2024
Non-compliance Consequences	Emails go to spam or get blocked	Emails go to spam or get blocked
Additional Recommendations	Use valid Reply-To, clean lists, honest headers	Use valid headers, permission-based sending, low spam complaints
Applies to Transactional Emails	Yes	Yes

Conclusion:

Microsoft’s introduction of new email authentication policies represent a significant advancement in email security and confidence in email communication.

It is, however, necessary to go beyond just adopting SPF, DKIM, and DMARC in order for your brand to truly stand out.

A DigiCert Verified Mark Certificate (VMC) will allow your logo to be authenticated to appear next to your emails, establishing awareness, trust, and engagement with your audience.

As inbox regulations become even more strict, the best strategy is to combine the solid technical standards with a visual means of trust.

Update your domain settings to comply with Microsoft’s changes, secure your domain, and implement a best practice in your email security strategy with the use of DigiCert Mark Certificates.

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