550 5.7.515 Access denied, sending domain does not meet the required authentication level
Outlook.com rejected unauthenticated bulk mail
Seen in Outlook.com, Hotmail, Live (Microsoft consumer mail)
Microsoft's consumer mail requires SPF, DKIM and DMARC for high-volume senders, and rejects mail that fails them.
Common causes
- Missing or failing SPF or DKIM for the From domain.
- No DMARC record (at least p=none) for the domain.
How to fix it
- Publish SPF and enable DKIM signing for every sending service.
- Publish a DMARC record and make sure messages align.
Got a different message? Paste it into the error explainer.
Related errors
- 550 5.7.26 Unauthenticated email is not accepted · Gmail rejected mail that failed DMARC
- 550 5.7.1 Relaying denied / Message rejected · The receiving server refused the message on policy grounds
- 421 4.7.0 Try again later · Temporarily deferred by the receiving server
- 550 5.7.23 SPF validation failed · The message failed the SPF check
- 550 5.7.509 Access denied, sending domain does not pass DMARC verification and has a DMARC policy of reject · Microsoft 365 rejected mail that failed DMARC
- 421 4.7.28 Our system has detected an unusual rate of unsolicited mail originating from your IP address · Gmail is rate limiting mail from your IP
- 550 5.7.1 Our system has detected that this message is likely unsolicited mail · Gmail blocked the message as spam
- 421 4.7.26 This mail has been rate limited because it is unauthenticated · Gmail deferred mail that passed neither SPF nor DKIM
- 421 4.7.27 Your email has been rate limited because SPF authentication didn't pass for this message · Gmail deferred or blocked mail that failed SPF
- 421 4.7.0 [TSS04] Messages from x.x.x.x temporarily deferred due to unexpected volume or user complaints · Yahoo is temporarily deferring your mail
- 550 5.7.25 The IP address sending this message does not have a PTR record · The sending IP has no reverse DNS
- 550 5.1.1 User unknown · The recipient address doesn't exist