SMTP code 550 DY-001
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.
This line comes from a knowledge base article on Microsoft, not on the standard.
- Meaning
- Mail from dynamic IPs is not accepted
- Next step
- Send from static IP space (Spamhaus PBL lists dynamic ranges)
From Microsoft Outlook.com Sender Requirements · SMTP error codes