SMTP code 550 5.7.626
What the knowledge base's own tables say about this code, and which articles say it — a description of the reply, never a placement prediction.
No article documents 550 5.7.626 itself. The lines below come from articles documenting 550 5.7.606-649, which covers it.
This line comes from a knowledge base article on Microsoft, not on the standard.
- Symptom
- NDR 550 5.7.606–649 Access denied, banned sending IP from a business or tenant recipient (a custom domain on Microsoft 365)
- System
- EOP (Office 365)
- Channel
- Delist portal https://sender.office.com