5.2.2 bounce: recipient mailbox full
5.2.2Mailbox fullPermanent: retrying will not help
552 5.2.2 <user@example.com>: Quota exceeded (mailbox for user is full)
What it means
RFC 3463 defines X.2.2 as "Mailbox full": the mailbox has hit its size or message count quota. RFC 5248 pairs it with basic code 552. The text in the example is the default Dovecot quota message; Gmail, Microsoft 365, and Yahoo each phrase it their own way but use the same code.
RFC 3463 says a full mailbox is a persistent transient condition, so the strictly correct form is 4.2.2, and many servers do return 452 4.2.2 or 4.2.2 inside a 552 reply. Your server then retries for days, and the final bounce you see may read 4.2.2 or 5.2.2 depending on how it reports expiry. Gmail and others send 552 5.2.2 straight away when the account has been full for a while.
It is different from 5.3.4 (the single message is bigger than the server allows) and 5.2.3 (the message is bigger than this mailbox’s per-message limit). With 5.2.2 a small message would fail too.
Likely causes
- The recipient has not cleared old mail and the mailbox reached its quota.
- Large attachments filled the mailbox quickly, including sent items and deleted items folders that count toward the quota.
- The account is abandoned, so nobody is emptying it.
- The admin set a low quota on a shared or service mailbox that receives automated mail.
How to fix it
- As the sender, tell the recipient through another channel that their mailbox is full, then resend once they have cleared space.
- Keep big attachments out of the retry; share a link instead so a nearly full mailbox can still accept the message.
- As the mailbox user, empty deleted items and sent items, and archive or remove large messages.
- As the admin, raise the quota or enable archiving, then confirm the server reports usage below the limit.
- If the address keeps bouncing with 5.2.2 for weeks, treat it as abandoned and stop sending to it from lists.
Checks that apply
- MX Lookup Identifies which provider hosts the mailbox, so you know whose quota rules apply.
- MailFlow Monitor After space is freed, confirms test mail is delivered again instead of bouncing.
FAQ
- Will my server keep retrying a full mailbox?
- If the reply was 4.2.2, yes, until the queue lifetime expires (often five days). A 5.2.2 reply stops retries immediately.
- Can I do anything as the sender?
- Only notify the recipient. The quota is on their side, so they or their admin have to free space.
- Why does a full mailbox hurt list senders?
- Mailbox providers treat repeated sends to long-full mailboxes like sends to abandoned addresses, a sign of poor list hygiene.