Exact response pattern
552 5.2.2 Mailbox fullPermanentGenericQuota
What it means
The recipient mailbox has exceeded its storage allocation.
Likely causes
- Recipient mailbox full.
Recommended response
- Stop repeated attempts according to policy.
- Do not classify as a sender reputation issue.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.