Exact response pattern
452 4.2.2 Mailbox fullTemporaryGenericQuota
What it means
The mailbox is over quota but the receiver treats the condition as temporary.
Likely causes
- Recipient storage quota exceeded.
Recommended response
- Retry for a limited period.
- Suppress only after the provider returns a permanent mailbox-full result or policy threshold is reached.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.