Docs
The emails sent out to the email addresses belonging to the iCloud.com domain are getting bounced due to this error - “5.2.2 <{xyz.icloud.com}>: the user is over quota”
Summary
The error message indicates that the quota of the recipient account is full and mail could not be delivered to that account. It can be solved by requesting your customer to “clean up” their mailbox and/or files he has stored on his account. Most of the time, this is caused by someone never deleting emails. It can be remedied by deleting old obsolete mail.
Solution
If the email sent out to your customers is failing to get delivered due to the issue - 5.2.2 xyz@icloud.com: the user is over quota, the error message indicates that the quota of the recipient account is full and mail could not be delivered to that account.
Every email account has a fixed data storage space allotted to it, referred to as the 'quota'. This quota limit is set when an email account is created.
If the customer's email belongs to iCloud; each iCloud account is allocated a certain amount of space, much like a drive on your computer. Once that space is filled up, there's no more room to accept any more, including email.
The solution to this is for the customer to “clean up” their mailbox and/or files he has stored on his account. Most of the time, this is caused by someone never deleting emails. It can be remedied by deleting old obsolete mail.
Unfortunately, you as the sender can't do anything, but contact the customer and let them know of the issue. Unfortunately, it is beyond the reach of Chargebee as well.
Articles & FAQ