Why do I get the following error trying to set up email in the Knox Workspace container - "Try again with network provider's default APN"

Samsung Devices with the default Email app.

The following error occurs gets when trying to set up email in the Knox Workspace: 'Try again with network provider's default APN'

[Root cause]
This issue occurs when the Email app cannot connect to the EAS activation server 

This is due to a settings issue with the Firewall, VPN or the Proxy server. Please check these settings and the issue should be resolved.