Email Knowledge Bounce codes

5.2.2 — Mailbox full (quota exceeded)

The enhanced status code 5.2.2 usually means the recipient’s mailbox cannot accept more mail because it has reached a storage limit. This is a permanent failure for that delivery attempt: the sender should not keep retrying forever without a change on the recipient side.

What 5.2.2 means

A mailbox has a quota: a maximum amount of storage or message count that the system allows. When that quota is exceeded, the receiving system may reject new messages and respond with 5.2.2. Some providers also use similar wording for “account over quota” or “insufficient storage” situations.

The bounce text often contains the most useful hint: it may explicitly say “mailbox full”, “quota exceeded”, “over quota”, or give a reference to a storage policy. When you see that wording, it’s almost always a recipient-side problem.

What it can look like

Action: failed
Status: 5.2.2
Diagnostic-Code: smtp; 552 5.2.2 Mailbox full
Action: failed
Status: 5.2.2
Diagnostic-Code: smtp; 552 5.2.2 Quota exceeded

Next steps

If you are the sender

The practical step is to contact the recipient (if possible) and ask them to free space or increase their quota. If you are sending from a system that maintains lists, treat repeated 5.2.2 bounces carefully: continuing to push mail into a full mailbox won’t succeed and can look like “noisy” behavior to providers.

If you are the recipient or mailbox admin

Free space (delete mail, empty trash, reduce large attachments), archive messages elsewhere, or increase the mailbox quota. If you run the mail system yourself, check whether the quota is real storage usage or a policy limit and adjust accordingly.

Related but different: 5.2.3 often means “message too large” (size limit), not “mailbox full”.

Related codes

5.2.3 (message too large), 4.2.2 (temporary mailbox full, if provided), and the full list: /bouncecodes/.