PowerDMARC

Microsoft Sender Requirements Enforced — How to Fix “550; 5.7.15 Access Denied” Rejections

Ahona Rudra
Microsoft sender requirements

From May 5, 2025, Microsoft is strictly enforcing its email sender requirements. This move requires anyone sending over 5,000 emails per day to Outlook.com, Hotmail, and other Microsoft consumer mailboxes to properly authenticate their messages. Failure to do so is triggering a “550 5.7.15 Access denied” error.

Post the May 5th deadline, this error code can be triggered by: 

Key Takeaways

  • Microsoft will reject emails from high-volume senders (>5,000/day) that lack proper authentication starting May 5, 2025.
  • Non-compliant emails will trigger the “550 5.7.15 Access denied” rejection error.
  • To comply, senders must correctly implement SPF, DKIM, and DMARC. 
  • Domain misalignment, or missing authentication records, will cause hard rejections. 
  • PowerDMARC can simplify compliance and ensure your messages reach Microsoft inboxes.

550; 5.7.15 Access Denied Error Code Explained 

SMTP error 550 5.7.15 is a permanent rejection error from Microsoft email services (like Outlook.com, Live, or Hotmail) that typically indicates that access is denied when attempting to send mail to a Microsoft consumer mailbox. If you are coming across this error, the reasons may be the following:  

1. Missing Authentication Records

Your high-volume email sending domain is missing the following email authentication protocols: 

  1. SPF (Sender Policy Framework): To authorize permitted senders for your domain. 
  2. DKIM (DomainKeys Identified Mail): To maintain email integrity and prevent tampering.
  3. DMARC (Domain-based Message Authentication, Reporting, and Conformance): To respond to unauthorized emails, increase visibility, and prevent spoofing. 

2. Alignment Issues

Alternatively, you may also be hit with the Microsoft 550; 5.7.15 error if your authentication protocols are not in proper alignment. According to the new high-volume sender requirements: 

  1. SPF must pass for the sending domain 
  2. DKIM must pass for the sending domain 
  3. DMARC must align with either SPF or DKIM (preferably both)

What Microsoft’s New Requirements Mean for Senders

Image source: Microsoft Tech Community

If you’re a high-volume sender, you must act now. Microsoft’s updated enforcement goes beyond simply flagging suspicious emails, it rejects them completely if they lack proper authentication.

While the initial plan was to direct non-compliant messages to recipients’ Junk folders, Microsoft revised its approach to address potential confusion and enhance security for users. On rejection, the error you’ll encounter looks like this:

550 5.7.15 Access denied, sending domain [SendingDomain] does not meet the required authentication level.

Steps to Fix Microsoft 550; 5.7.15 Access Denied Error

To fix the 550; 5.7.15 error follow these steps:

1. Enable SPF 

Sign up with PowerDMARC to use our free SPF generator tool. This tool will help you create an instant SPF record – ready to be published in your DNS. 

2. Implement DKIM 

You can use our DKIM generator tool to create an error-free DNS record that can be directly published on your domain. 

3. Configure DMARC 

Once you are done implementing SPF and DKIM, you can now focus on DMARC. To enable DMARC: 

DMARC record examples:

Baseline DMARC setup: v=DMARC1; p=none; 

Recommended DMARC setup: v=DMARC1; p=reject; rua=mailto:rua@company.com;

Note: PowerDMARC recommends starting with a “none” policy to monitor emails, then gradually moving to “quarantine” and “reject” for stronger protection against email threats.

  1. Additional Recommendations

Additional email hygiene recommendations include:

Check Your Domain’s Compliance 

How PowerDMARC Helps

Use PowerDMARC to simplify setup, monitor authentication status, and enforce policies with ease.

Manually setting up SPF, DKIM, and DMARC can be technically challenging, time-consuming, and error-prone. This may result in lost business opportunities and damaged sender reputation. PowerDMARC simplifies compliance with: 

Start your 15-day free DMARC trial with PowerDMARC today! 

Final Thoughts 

The May 5, 2025 deadline is fast approaching. If you’re a high-volume sender, inaction means losing access to Microsoft inboxes. Don’t wait for the 550 5.7.15 rejection to hit your logs. Act now by setting up your email authentication today and stay deliverable, trusted, and secure.

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