5.2.2 SMTP bounce: mailbox full
What 5.2.2 means
The recipient mailbox is over its quota and the receiver rejects the message for this attempt. Recipient storage must be freed before delivery can succeed.
Message text
Mailbox full
Common causes of 5.2.2
- Recipient mailbox quota is full
How to fix 5.2.2
- Ask the recipient to free mailbox space.
- Reduce message size if the mailbox has only a little room.
- Do not resend unchanged until space is freed.
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How to read 5.2.2
The second part, 5.2.2, is an enhanced status code (RFC 3463 §2) written class.subject.detail. Class 5 is a Permanent failure (5xx): the command was rejected and the sender should not repeat it unchanged (RFC 5321 §4.2.1; RFC 3463 §2).. Subject 2 is mailbox: a problem with the recipient mailbox, such as full, disabled or unknown. The detail number refines the subject, and providers may define details of their own, which is why one code can read differently at Gmail, Microsoft and Yahoo.
Do not keep resending the same message: a permanent failure repeats until the cause is fixed. Correct the cause, then send a new message.
Official source: www.rfc-editor.org. Last verified 2026-10-20.
Related guides
- How to create an SPF record (syntax and examples)
- How DKIM works and how to publish a DKIM record
- How to set up a DMARC record, from p=none to p=reject
Related codes
- 5.2.3 SMTP: message too large
- 550 SMTP: mailbox unavailable
- 551 SMTP: user not local
- 552 SMTP: storage exceeded
- 553 SMTP: mailbox name not allowed
- 554 SMTP: transaction failed
FAQ
What does 5.2.2 mean?
The recipient mailbox is over its quota and the receiver rejects the message for this attempt. Recipient storage must be freed before delivery can succeed. This is a permanent failure.
How do I fix 5.2.2?
Ask the recipient to free mailbox space. Reduce message size if the mailbox has only a little room. Do not resend unchanged until space is freed.
Is 5.2.2 permanent, and should I retry?
5.2.2 is a permanent failure, so retrying the same message will fail again. Fix the cause first, then send a new message.