Proxy pass allows you to forward requests from a perimeter Apache server (a proxy or gateway) to an internal web server. In this case, we'll be forwarding Microsoft Active Sync from an Android smartphone, configured to use Corporate email, to Zentyal/SOGo, using Apache. In this example, we'll be using internal.server.tld as our hostname. Substitute your own hostname, in its place. 

If you have a Zentyal or SOGo install, that you would like to tie to your main domain, here is how you do it.

This example assumes you're going to replace http://internal.example.com  with your own internal server. So, to sum this up, we're going from the
client computer -> proxy server -> internal Zentyal/SOGo server. 

A couple weeks ago, a small business customer approached me with an issue. They needed to share files across 6 to 7 computers. The problem is, they only have a workgroup setup. There is not a means of pulling central authentication.