552 5.2.2: mailbox full
The recipient's mailbox is over its storage quota, so the message was refused. It will work again once the recipient clears space.
552 5.2.2 The recipient's inbox is out of storage space and inactive.
Start of Gmail's text, as listed in Google's SMTP errors reference.
What 552 5.2.2 means
RFC 3463 defines X.2.2 as "Mailbox full": the user has exceeded a per-mailbox administrative quota or physical capacity, and the recipient can delete messages to make space. RFC 3463 adds that the code should be used as a persistent transient failure, and the IANA registry lists 552 as its usual basic code.
That combination is a little contradictory: 552 is a permanent reply, while the enhanced code describes something the recipient can fix. Servers differ. Gmail uses 452 4.2.2 ("The recipient's inbox is out of storage space") as a temporary deferral, and 552 5.2.2 for an inbox that is out of storage space and inactive. With a 452 your server keeps retrying; with a 552 your message bounced.
Microsoft 365 uses the number 5.2.2 for something unrelated in its own documentation: "Submission quota exceeded", when a sender passes Exchange Online's sending limits. If the bounce mentions a submission quota, it's about your sending, not the recipient's storage.
Likely causes
- The recipient's mailbox is over its storage quota.
- The account is inactive and nobody is clearing it.
- Shared storage (for example mail plus files) is full.
How to fix it
If you sent the message
- Contact the recipient another way and resend after they clear space.
- If the bounce mentions a submission quota instead, your account hit a sending limit; wait and reduce your sending rate.
If you're the recipient or their admin
- Delete large or old messages and empty the deleted items folder.
- Archive older mail or ask your admin for more storage.
- If the account is unused, have the admin set up forwarding or close it.
Frequently asked questions
Will my message be delivered when the recipient frees up space?
Only if the server deferred it (a 452 4.2.2) and your server is still retrying. A 552 5.2.2 is a bounce, so you need to resend once the recipient has made room.
Can I tell how full the recipient's mailbox is?
No. The error only says the quota was exceeded. The recipient or their admin can check the mailbox size.
Sources
- RFC 3463: Enhanced Mail System Status Codes
- Gmail SMTP errors and codes (Google Workspace Admin Help)
- Email nondelivery reports (NDRs) and SMTP errors in Exchange Online (Microsoft Learn)
Provider messages are quoted as the provider publishes them. Servers can change their wording, so the bounce you received may differ slightly.
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