SMTP code X.6.7
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.
- Meaning
- Non-ASCII addresses are not permitted for that sender or recipient
- Typical basic codes
- 550, 553
From SMTPUTF8 / Internationalized Email (RFC 6530/6531/6532) · Relay and fallback rules, and error codes