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Deliverability Letter

452 4.2.2

452 4.2.2 Mailbox Full

Mailbox Full

The recipient mailbox is out of storage space.

Gmail refuses new mail when the account hits its quota. It is a temporary condition that should clear once the user frees up storage.

Severity

WARNING

Provider

Gmail

Reference

Mitigation Portal

Last Reviewed

2025-06-01

How to Fix 452 4.2.2

Follow these steps to resolve this Gmail SMTP error and restore normal delivery.

  • ✓Retry delivery for a few days before suppressing the address.
  • ✓Encourage contacts to upgrade or free space if the relationship warrants it.
  • ✓Stop sending marketing drips to mailboxes that stay full for weeks.
  • ✓Use engagement scoring to prioritise retries for VIP recipients.

Helpful Resources

More Gmail SMTP Codes

Keep these related troubleshooting guides handy while addressing 452 4.2.2.

550-5.1.1 – 550 5.1.1 Recipient Address Does Not Exist
ERROR
550 5.1.0 – 550 5.1.0 User Unknown
ERROR
550 5.2.1 – 550 5.2.1 Mailbox Disabled
WARNING
421 4.7.0 – 421 4.7.0 Temporary System Problem
WARNING

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