What is “over quota”?

• Over quota indicates mailbox storage exhausted:
• What it means:
• Recipient has used all allocated storage. No space for new messages. Message cannot be delivered.
• Typical codes:
• 452 (temporary) or 552 (permanent). 5.2.2 or 4.2.2 enhanced codes. "Mailbox full" or "over quota" in message.
• Why mailboxes fill up:
• Heavy email volume. Large attachments accumulated. User does not manage inbox. Free tier with limited storage.
• Handling:

452: Treat as soft bounce, retry. 552: May indicate persistent issue. Multiple consecutive failures: Consider suppression.

• Signals about recipient:
• May indicate inactive or abandoned mailbox. User may not be managing email. Questionable address quality.
• Over quota is a full cargo hold. No new deliveries until space is cleared.