# 552 5.2.2: mailbox full

URL: https://iblockspam.com/smtp-errors/552-5-2-2
Last updated: 2026-10-09

Code: 552 5.2.2 (permanent failure, the message bounced)
Provider: Standard (RFC)

The recipient's mailbox is over its storage quota, so the message was refused. It will work again once the recipient clears space.

What the bounce says:

```
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.

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.

## Common 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 (sender)

- 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.

## How to fix it (recipient or 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.

**Q: 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.

**Q: 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: https://www.rfc-editor.org/rfc/rfc3463
- Gmail SMTP errors and codes (Google Workspace Admin Help): https://knowledge.workspace.google.com/admin/support/troubleshooting/gmail-smtp-errors-and-codes
- Email nondelivery reports (NDRs) and SMTP errors in Exchange Online (Microsoft Learn): https://learn.microsoft.com/en-us/troubleshoot/exchange/email-delivery/ndr/non-delivery-reports-in-exchange-online

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