Emails sent out to the customers are getting bounced due to this error - "5.2.2 : user is over quota". Why?

Problem Statement

This article explains why emails bounce with the "5.2.2 : user is over quota" error (common with iCloud addresses) and how to resolve it.

Solution

This error means the recipient's email account has reached its storage limit (quota). Mail cannot be delivered until space is freed.

Cause

Every email account has a fixed storage quota. When it is full (e.g., iCloud storage), no new messages can be accepted. This often happens when the recipient rarely deletes emails.

What the customer must do

Ask the customer to clean up their mailbox and stored files. Deleting old or unnecessary emails usually resolves the issue.

What you can do

As the sender, you cannot fix this. Contact the customer and explain the issue. Chargebee cannot resolve it either; the recipient must free up space in their account.