Generic SMTP mailbox error

SMTP 5.2.2: recipient mailbox full

5.2.2 means the recipient mailbox has exceeded its storage allocation. The recipient or their administrator owns the fix; changing sender authentication or DNS is unrelated.

Problem description

A receiver may return:

552 5.2.2 Mailbox full

Diagnostic availability: MailFixIt does not access mailbox quota or recipient accounts. Contact the recipient through another channel.

Is this temporary or permanent?

The 5.x.x code rejects this attempt. Capacity can change, so a new attempt may work after the recipient frees storage or an administrator raises quota.

What the recipient should check

Mailbox and cloud-storage quota.
Deleted-items and recoverable-items retention.
Archive, journaling, or retention policy behavior.
Account/license state and organization limits.

Sender response

Stop high-frequency retries.
Notify the recipient through another trusted channel.
Retain the bounce timestamp and exact address.
Send a fresh message after the recipient confirms capacity.
Remove persistently invalid recipients from automated lists.

Providers may pair mailbox-full text with different basic SMTP reply codes. Use the complete response and provider guidance when available.

Frequently asked questions

What does SMTP 5.2.2 mean?

The recipient mailbox is full or over its storage allocation.

Who can fix a full mailbox?

The recipient or their email administrator must free storage or increase quota.

Is this related to SPF or DKIM?

No. Sender authentication changes do not create recipient storage capacity.

Related email diagnostics

Primary sources: IANA SMTP Enhanced Status Codes registry and RFC 3463.