Generic SMTP delivery response
Resolve SMTP 4.2.2: Recipient mailbox full
The recipient mailbox exists but cannot accept more mail because its quota or storage capacity is exhausted.
A representative response is:
4.2.2 Mailbox full.
This is normally temporary. Let the sending server retry while the recipient or administrator restores mailbox capacity.
What this response means
Standard enhanced status 4.2.2 means the recipient mailbox is full. The message is valid, but delivery is delayed until storage becomes available.
What to do
- Leave the message in the outbound queue and allow normal retries with backoff.
- Contact the recipient another way and ask them to remove mail or files, empty deleted items, or request more quota.
- If you administer the mailbox, check the actual mailbox and archive quotas, retention state, and storage service health.
- After capacity is restored, let the queued message retry or send one new test.
- If the full response names a different condition, follow that provider-specific wording instead of the generic interpretation.
Changing the sender’s SPF, DKIM, DMARC, or MX records cannot increase a recipient mailbox quota.
Who can fix it
The recipient or the administrator of the receiving mailbox service owns the repair.
Related troubleshooting
Use other recipient-status guides only if the code or full response changes.
Frequently asked questions
What does SMTP 4.2.2 mailbox full mean?
The mailbox exists but has exceeded its storage quota or physical capacity. The recipient or mailbox administrator controls the fix.
Can MailFixIt prove this entire bounce from public DNS?
No. The current checker can evaluate selected public DNS configuration, but it cannot recreate recipient state, credentials, reputation, message content, or a historical provider SMTP decision.
Related email diagnostics
Primary sources: IANA SMTP Enhanced Status Codes.