Exact response pattern
550 5.6.4 Conversion with loss performedPermanentGenericContent
What it means
The system reports a content conversion problem that would lose information.
Likely causes
- Incompatible content format.
Recommended response
- Regenerate using compatible MIME.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.