SMTP codes
SMTP 5.4.1 Recipient address rejected / no answer
Microsoft 365 “Access denied”: the recipient domain is not accepted by this server (often a misconfigured MX or Directory-Based Edge Blocking).
- Class
- 5xx · Permanent failure
- Retried?
- No, the message bounces
- Defined in
- RFC 7372 / provider
What to do
- Check the address; the recipient’s admin should check accepted domains and MX.
How it appears in a bounce
550 5.4.1 Recipient address rejected / no answer
Paste the full bounce into the decoder — it finds every code and recipient and says what to check.