550 5.7.515 is a permanent SMTP reply meaning outlook.com: sender does not meet the authentication level. Microsoft counts a domain as high volume when it sends 5,000 or more messages a day to its consumer mailboxes. Those senders must pass SPF, pass DKIM, and publish DMARC (at least p=none) that aligns with SPF or DKIM.
What 550 5.7.515 means
Microsoft counts a domain as high volume when it sends 5,000 or more messages a day to its consumer mailboxes. Those senders must pass SPF, pass DKIM, and publish DMARC (at least p=none) that aligns with SPF or DKIM.
Common causes
DMARC is missing for the From: domain
Most commonSPF and DKIM pass, but there is no record at _dmarc, so the domain does not meet the rule.
DKIM is missing or not aligned
Most commonThe ESP signs with its own domain, so DKIM does not match your From: domain.
SPF fails for the sending service
CommonA new platform is sending and is not in your SPF record.
How to fix 550 5.7.515
- 1
Pass SPF and DKIM for your own domain
Set up domain authentication in each sending platform, and add each one to your single SPF record.
- 2
Publish DMARC
Add v=DMARC1; p=none; rua=mailto:you@yourdomain at _dmarc. Microsoft asks for p=none at least, aligned with SPF or DKIM.
- 3
Check every domain you send from
Run a free EmailHealth check on each From: domain. Teams with many sending domains can watch all of them daily.
Confirm your domain is set up correctly
Most delivery failures — permanent or temporary — trace back to authentication or reputation. Run a free EmailHealth check to confirm SPF, DKIM, DMARC, blacklist status, and TLS are all healthy for your sending domain. If you send in volume, free daily monitoring will alert you before a small issue becomes a flood of bounces.