Exact response pattern
452 4.2.2 The email account that you tried to reach is over quotaTemporaryGmailQuota
What it means
The recipient account is temporarily unable to accept mail because of quota.
Likely causes
- Recipient storage is full.
Recommended response
- Retry for a limited period.
- Do not blame sending IP reputation.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.