Exact response pattern
550 5.3.4 Message too big for systemPermanentGenericContent
What it means
The destination system cannot accept a message of this size.
Likely causes
- Message exceeds server maximum.
Recommended response
- Reduce the MIME size and retry as a new message.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.