Email replies are failing to be delivered

Email replies are failing to be delivered

I have sent many emails through Zoho using with a reply to my business account. However, the replies are not being delivered. I am getting the following message:

"Your mail message to the following address(es) could not be delivered.
This is a permanent error. Please verify the address(es) and try again.

< info@snapasong.com >:
child status 100...The e-mail message could not be delivered because the user's mailfolder is full."

How can I fix this??