If there is still space on the server, then log into CPanel and go to email accounts to increase the mailbox size.
If your mailbox is full then the solution is to upgrade your package or to delete old emails.
Please feel free to contact our hosting department if you require further assistance.
If you require further assistance, please
send a message to our WhatsApp helpline: https://whatsapp.afrihost.com
or visit our Help Centre: https://help.afrihost.com/
or see our FAQ page: http://faq.afrihost.com