On May 5, 2025, Microsoft began rejecting all emails that fail DMARC, SPF, or DKIM authentication. If you’re encountering the following error:

550 5.7.515 Access denied, sending domain [YourDomain] does not meet the required authentication level.

This means your domain is  non-compliant, and your emails are being blocked from reaching Outlook, Hotmail, or Live.com inboxes.

Here’s how to fix it—and how Skysnag can fully automate your compliance.

Why This Error Happens

Microsoft’s enforcement is part of a larger shift across the email ecosystem. If your domain isn’t fully authenticated with SPF, DKIM, and DMARC, Microsoft sees your email as untrustworthy—and drops it.

Step 1: Diagnose the Problem

The first step is understanding where your configuration is failing. You can check instantly using Skysnag:

Run a 30-Second DMARC Check

We’ll tell you whether:

• SPF is valid and aligned
• DKIM is signing properly
• DMARC is published correctly
• Your reporting addresses are functional

Step 2: Correct Your DNS Records

SPF – Sender Policy Framework

• Define all servers allowed to send mail for your domain.
• Example: v=spf1 include:mail.yourprovider.com ~all

DKIM – DomainKeys Identified Mail

• Enable DKIM in your email provider and publish your public key.
• Skysnag validates and monitors DKIM key alignment and health.

DMARC – Domain-Based Message Authentication

• Publish a DMARC record in your DNS.

Want it done right?

Skysnag’s platform automates the entire setup, ensuring accurate SPF flattening, key rotation, and alignment validation.

Start your free trial →

Step 3: Monitor, Maintain, and Comply Automatically

Fixing it once isn’t enough.

DMARC requires ongoing validation. IPs change. Records drift. Vendors misconfigure.

Skysnag monitors your domain continuously for:

• Misalignments
• Broken reporting destinations
• Third-party abuse
• Policy enforcement gaps

You get full visibility and alerts before anything fails.

See how Skysnag Protect works

Step 4: Microsoft-Specific Considerations

Microsoft expects DMARC to pass and be aligned. Having a p=none policy with failing SPF/DKIM is no longer tolerated.

Rejected messages will not reach the inbox or junk folder. They’re simply blocked.

To stay compliant:

• Move from p=none to p=quarantine or p=reject gradually.
• Use Skysnag’s automated policy recommendations to transition safely.

Final Thoughts

The 550 5.7.515 rejection is not a glitch. It’s your wake-up call to secure your email infrastructure.

Non-compliance means:

• Dropped email
• Damaged sender reputation
• Missed business opportunities

Skysnag handles all of it—SPF, DKIM, DMARC, MTA-STS, TLS-RPT, and BIMI.

• Fix email rejection
• Prevent spoofing
• Protect your brand
  

You might be interested in reading:

Microsoft Email Rejections Explained: 550 5.7.515… May 1, 2025

Ten DMARC myths ready to be debunked  September 7, 2023