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452 4.2.2: Recipient's mailbox is full

The recipient is out of storage. Their mailbox exists but can't accept new mail until they free up space.

Bounce type
Soft bounce (temporary)
What to do
Retry later
Returned by
Gmail / Google Workspace; Any mail server

What 452 4.2.2 means

4.2.2 is 'Mailbox full' in RFC 3463: the user is over their storage quota. RFC 3463 says it should be used as a transient failure, because the recipient can delete mail to make room. Gmail returns it when the recipient's Google storage (shared across Gmail, Drive and Photos) is full.

For cold email, a full mailbox is a signal about the lead. Active users clear space quickly. A mailbox that stays full for weeks is often abandoned.

What the bounce looks like

The wording providers document for this code. Your bounce may add an IP address, a session ID or a help link after it.

Gmail
452 4.2.2 The recipient's inbox is out of storage space. Please direct the recipient to Manage files in your Google Drive storage.

Why cold emailers see 452 4.2.2

  • The recipient has used all their storage quota.
  • The account is abandoned and has been filling up with unread mail, which is common for old addresses in purchased or scraped lists.

How to fix 452 4.2.2

  1. Let your server retry for its normal window (often up to several days).
  2. Don't resend manually; the problem is on the recipient's side.
  3. Track repeat offenders. If the same address returns 'mailbox full' across several campaigns, suppress it.

Will it retry on its own?

Retry, then suppress if it persists. One 452 4.2.2 is fine. Repeated over-quota errors (or Gmail's permanent 552 5.2.2 'out of storage space and inactive') mean the address is effectively dead.

Reading the code

The basic code 452 means "Insufficient system storage (temporary)" under RFC 5321. In 4.2.2, the 4 is the class (persistent transient failure) and the 2 is the subject (mailbox). The detail number 2 is registered in RFC 3463 / the IANA registry as "Mailbox full".

Class 4
Persistent transient failure
A temporary condition delayed delivery. The message itself is valid, and sending again later may succeed.
Subject 2
Mailbox
A problem with the recipient's mailbox, such as full or disabled. Under the recipient's control.
Detail 4.2.2
Mailbox full

Check the rest of your setup

Paste the headers of a message that did get through into the email header analyzer to confirm SPF, DKIM and DMARC pass, and check your domain with the SPF, DKIM & DMARC checker. The deliverability checklist covers the rest of a healthy sending setup.

Got a different bounce? Paste it into the SMTP error code lookup to decode it.

FAQ

Is 452 4.2.2 a hard bounce or a soft bounce?

452 4.2.2 is a temporary failure (a soft bounce). Your sending server should retry automatically, and the message is often delivered on a later attempt. If it keeps failing for days, the server gives up and reports a final bounce.

Should I remove the contact after a 452 4.2.2 bounce?

No. Retry, then suppress if it persists. One 452 4.2.2 is fine. Repeated over-quota errors (or Gmail's permanent 552 5.2.2 'out of storage space and inactive') mean the address is effectively dead.

What does 4.2.2 mean in the error code?

In 4.2.2, the 4 is the class (persistent transient failure) and the 2 is the subject (mailbox). The detail number 2 is registered in RFC 3463 / the IANA registry as "Mailbox full".

Related SMTP codes

See all SMTP error codes

Sources

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