5.2.2Recipient mailbox is full

The recipient mailbox has exceeded its assigned quota or reached physical capacity. Code 5.2.2 is a permanent failure, so do not retry the same unchanged send.

The X.2.2 pattern means that the mailbox is full because its user exceeded a per-mailbox administrative quota or its physical capacity. The standard indicates that the recipient may make space by deleting messages. The concrete 5.2.2 code combines this meaning with permanent class 5.

The leading digit 5 denotes a permanent failure of the current send. Although the recipient or administrator may later free space, the same attempt should not be retried without a confirmed change that removes the cause.

Class

Permanent failure

Retry

Do not retry unchanged

Suppression

Check the full context

Operational guidance: stop automatic and manual retries of the unchanged send. Consider a new attempt only after the recipient or administrator confirms that space has been freed or the applicable quota has been changed.

Operational guidance: inspect the full response, exact address, delivery history, and local policy before deciding suppression. Code 5.2.2 alone does not justify automatically suppressing the address or its entire domain because the capacity condition may later change.

• The recipient exceeded the administrative quota assigned to the mailbox.
• The mailbox reached its available physical capacity.

1. Inspect the raw SMTP response or delivery report and confirm the exact 5.2.2 code and a basic reply in the 5xx class.
2. Correlate the result with the intended message, attempt time, and exact recipient address; do not infer the product or mailbox type from the code alone.
3. Ask the recipient or their administrator to inspect the quota and capacity of that mailbox and confirm whether space has been freed.
4. Retain the full response and record the confirmed state change before preparing a new send; do not retry without such a change.

The only accepted Microsoft example uses the exact response: “554 5.2.2 mailbox full; STOREDRV.Deliver.Exception:QuotaExceededException.MapiExceptionQuotaExceeded”. The example maps to canonical code 5.2.2 and the meaning “mailbox full.” It shows provider practice rather than extending the standards definition.

554 5.2.2 mailbox full;
STOREDRV.Deliver.Exception:QuotaExceededException.MapiExceptionQuotaExceeded

Compare 4.2.4, which means a temporary mailing-list expansion problem, and 5.2.3, which concerns a per-mailbox administrative limit on the length of an individual message. Both describe conditions different from the lack of space represented by 5.2.2.

• 4.2.4Temporary mailing-list expansion problem
• 5.2.3Message exceeds the mailbox limit

The X.2.2 meaning and the permanent class of the concrete code were verified against the IANA registry and RFC 2034, RFC 3463, and RFC 5248; the exact Microsoft example comes from accepted evidence p03-b02-microsoft-x-2-2-001. Retry and suppression guidance, diagnostics, and owner actions are operational recommendations distinct from standards facts and provider practice. The sources were verified on July 17, 2026.

• iana-smtp-enhanced-status-codesT0 source

  Enumerated Status Codes / X.2.2

• rfc5248T0 source

  Section 2.1: registry fields and non-exclusive Associated Basic Status Code

• rfc2034T0 source

  Section 4: enhanced status class agrees with SMTP reply class

• rfc3463T0 source

  IANA registry reference for X.2.2

• p03-b02-microsoft-x-2-2-001T1 source

  Symptoms > Diagnostic information for administrators > Remote Server returned block

Last verified: 17 July 2026