Problem
SMTP 5.2.2 Error when sending an email, What does it mean?
Solution
What causes SMTP 5.2.2 errors?
SMTP error 5.2.2 is returned when an email cannot be delivered because the recipient’s mailbox has exceeded its storage quota.
This means the receiving mailbox is full and cannot accept any new messages until space is freed.
Note, This is a permanent delivery failure for that specific message at that time. The email will not be delivered unless the recipient resolves the storage issue or their mailbox quota is increased.
Common reasons for SMTP 5.2.2 (Mailbox Full)
Typical causes include:
- Recipient mailbox storage limit has been reached
- Email account has not been accessed or maintained
- Large attachments filling mailbox capacity
- Corporate or hosted mailbox quotas being exceeded
- Legacy or unmanaged email accounts with strict limits
How to fix SMTP 5.2.2 error
However, the following actions can help resolve or work around the issue:
1. Contact the recipient
Inform the recipient that their mailbox is full so they can delete old messages or increase storage.
2. Try an alternative contact method
If the message is urgent, contact the recipient via another email address or communication channel.
3. Retry later
Once the recipient has freed up mailbox space, the email can usually be delivered successfully on resend.
4. Reduce email size (preventative)
If large attachments are contributing to delivery issues, consider:
- Using file links instead of attachments
- Compressing files before sending
When SMTP 5.2.2 errors keep happening
If you consistently receive 5.2.2 errors when emailing the same domain or recipient, it may indicate:
- The recipient account is inactive or abandoned
- The mailbox is permanently over quota
- The organisation’s email system has strict storage limits
How to reduce delivery issues caused by mailbox full errors
While SMTP 5.2.2 errors are controlled by the recipient, you can reduce impact by:
- Keeping recipient lists up to date
- Removing inactive email addresses
- Using email validation tools for bulk sending
- Avoiding unnecessary large attachments
