There can be many reasons why emails are not being delivered to your address. Reasons vary from the spam filter blocking these mails or the server delivering them to the incorrect folder.
Your best option is to contact Afrihost Support as they will be able to to assist. They have access to the spam filter and server logs and can determine if the mails are in fact reaching the server.
If you are receiving a bounce back email to these Gmail and Yahoo accounts please provide it too as this contains valuable information that may assist in resolving the issue.
You can contact Afrihost Support on 011 612 7200 or use their Live Chat service