Thank you for your question. It sounds like you are reaching your mailbox quota. The quota is set when you create an email account, and there is no hard limit.
Here is a link to an article on how to increase your quota in the cPanel.
If you have any further questions, feel free to post them below, or contact live Tech Support.
They are available 24/7 via:
Phone: 877-595-4482 x2
Chat (there is a link on the top right).
|Email:||support@WebHostingHub.com||Ticket:||Submit a Support Ticket|
|Chat:||Click To Chat Now|