Outlook / Hotmail "550 5.7.515 Access denied, sending domain does not meet the required authentication level"

What's happening: Since May 2025 Microsoft rejects high-volume mail to outlook.com, hotmail.com and live.com unless the From domain passes SPF and DKIM and has a DMARC record (p=none is enough). 5.7.515 means one of those three is missing or failing.

How to fix it

1. Publish one SPF record covering every service that sends as your domain.
2. Enable DKIM in each sending tool (Microsoft 365: Defender portal → Email authentication settings → DKIM → enable for your domain, after publishing the two CNAME records it shows).
3. Publish DMARC at _dmarc.yourdomain.com, at least v=DMARC1; p=none, and make sure SPF or DKIM aligns with your From domain (same domain, not the tool's own domain).
4. Resend. If it still bounces, check the bounce for which domain failed: often it's a tool sending with its own return path and no custom DKIM.

Not sure which record is wrong? Check your domain free: it shows which of SPF, DKIM and DMARC is failing, in 5 seconds, no signup.

Other fix guides

• Gmail 550 5.7.26 "sender is unauthenticated"
• SPF permerror: too many DNS lookups
• Multiple SPF records found
• "dmarc=fail" in headers
• "dkim=none" / DKIM not set up
• Gmail "via" another domain next to your name
• "blocked using Spamhaus" bounce
• Emails going to spam or junk (general)