Exact response pattern
550 5.6.1 Media not supportedPermanentGenericContent
What it means
The receiver does not support the message media or conversion required.
Likely causes
- Unsupported body type.
Recommended response
- Send standards-compliant MIME content.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.