Enhanced SMTP status code · RFC 3463 · IANA
5.2.2 Mailbox full
The recipient has exceeded their space or quota. They can make room by deleting mail, so the error is usually temporary.
- Class: Permanent failure
Class 5: a permanent failure. Resending the same message will not help: something about the message, the sender or the destination must change (RFC 3463 §3.1). The registry says this code is only useful as a temporary failure.
Also seen as:
4.2.2 - Subject: X.2 · Mailbox
Something about the recipient's mailbox; under the recipient's control.
- Associated basic codes (IANA registry)
How 5.2.2 appears at providers
The exact text from the provider's documentation, as you see it in the bounce, and what it means.
Gmail
-
552 5.2.2
The recipient's inbox is out of storage space and inactive.
The recipient's mailbox is full and inactive, so the message cannot be delivered.
-
452 4.2.2
The recipient's inbox is out of storage space.
The recipient's mailbox is out of storage. Only the recipient can make room; the sending server retries for a while.
Microsoft 365 / Exchange Online
-
5.2.2
Submission quota exceeded
The sender exceeded Exchange Online's recipient or message rate limit.
Have the whole error message?
Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026