The following article will show you how to white-list and also blacklist email accounts & IP addresses.
Let's take a look at the instructions below:
1. The first thing you'll want to do is log in to your webmail account by going to mail.domain.co.za and in the upper right-hand side after logging in - next to your username/email address click the drop-down to access the Settings menu.
2. In the left pane, click Spam Settings.
3. Click either the Blacklist tab or the white-list tab
4. Click add and enter the domain / email address or IP address that you wish to black/white-list
NOTE: You will no longer receive emails from the specified domain/ email or IP if blacklisted and will ALWAYS receive emails from the specified domain/ email or IP if white-listed.