The recipient mailbox has exceeded its storage limit and cannot accept new messages. This is a temporary failure that may resolve when the recipient frees up space by deleting old emails.
What Does Error 422 Mean?
SMTP code 422 indicates the recipient's mailbox has reached its storage quota and cannot accept additional messages. This is functionally similar to enhanced code 4.2.2 and is treated as a soft bounce because the condition may be temporary - the recipient might delete messages to free up space.
While individual 422 bounces are common and not alarming, consistently bouncing to the same address with 422 suggests the mailbox may be abandoned. After 3-5 consecutive soft bounces to the same address over several days, most email best practices recommend suppressing that address to protect your sender reputation.
Common Causes
- Recipient mailbox has reached its storage quota
- Mailbox is abandoned and has filled up over time
- Recipient receives high volume of email without cleaning up
- Organization has set restrictive mailbox size limits
How to Fix Error 422
- Retry delivery after a delay - the recipient may free up space
- Suppress the address after 3-5 consecutive soft bounces over multiple days
- Contact the recipient through another channel to alert them
- Review your list for inactive addresses that consistently return 422
Frequently Asked Questions
SMTP error 422 means the recipient's mailbox has exceeded its storage limit and cannot accept new messages. The email server is rejecting your message because the specific recipient's account is over quota. This is a mailbox-level storage issue, not a server-wide problem. Your message will not be delivered until the recipient frees up space in their mailbox.
As a sender, you cannot directly fix this error because the recipient's mailbox is full. Contact the recipient through an alternative channel (phone, text, or messaging app) and let them know their email storage is full. Suggest they delete old emails and empty their trash folder. You can retry sending after they have freed up space. If this is a recurring issue, consider sending smaller messages without large attachments.
SMTP 422 can be treated as a temporary error, since the delivery failure may resolve once the recipient clears mailbox space. However, most sending servers will not automatically retry 4xx errors indefinitely. If the recipient does not manage their storage within the retry window (typically 3-5 days), the message will permanently bounce. For marketing emails, repeated 422 errors from the same address indicate an inactive or abandoned mailbox that should be removed from your list.