This courtesy article will show you how to connect your remote users to your company's Exchange server. This article is written with a few considerations to keep in mind. No warranty is available on this solution. If you are not comfortable with your server configuration skills (namely DNS), do not attempt this configuration.
This is more of a small business solution. The setup implies you're running an all-in-one server, such as MS SBS 2003. You'll need Active Directory, DNS, and Exchange on the same machine to follow this verbatim, and they need to be working properly beforehand. If they are on multiple servers, Hamachi needs to run on all of them. This should be the only difference, as the rest is done behind the scenes by DNS, but this configuration is untested.
Exchange is a talkative application. Ensure your business's Internet connection can handle the increased upload capacity. I.E., running 1.5 MB DSL with a 384 Kbit upload cap will not cut it. It will bring your Internet connection to its knees when you start adding multiple concurrent users, especially when emails with attachments are introduced. Stick with OWA in this case, or upgrade your connection.
First, install Hamachi on your server(s), and on any client machine needing to connect to it for email. Ensure that everything has green indicators on their Hamachi lists. Also, you will need to run Hamachi as a service on at least the server(s). This will ensure you don't have to leave it logged in, or in a locked state to allow users to connect, which is a security risk. Once this part is all set, you can, test the connections. Make sure you can ping the computers both ways; server to client and client to server, server to server, and all the connection status indicators for each peer are Green.
You need to create a reverse lookup zone for the Hamachi 25.x.x.x network. To do this, start the Reverse Lookup Zone wizard in DNS. The network is 25. , notice there is nothing after 25. , this is important. This is because Hamachi uses a classful subnet in the Class A range (25.x.x.x). All of the other lookup zone settings can be left as the default, or customized to your particular needs. Once this is done, create a PTR record that resolves a pseudo server name to the server's Hamachi IP. DO NOT point the server's real name to the Hamachi IP. This WILL cause issues if you have local Exchange, AD, and DNS users on the same network as the server(s). Now, go into your Forward Lookup Zone and create a host (A) record for the same pseudo server name and Hamachi IP. This should complete the server setup. Use NSLOOKUP to ensure the DNS can resolve the Hamachi IP's to their pseudo hostnames.
Client Set Up
You need to ensure that your computers can resolve the server hostname over the Hamachi connection. To do this, open TCP/IP properties of the Hamachi adapter, and point the default DNS server to the server's Hamachi IP address. You'll also want to make sure you put a manual host entry into your HOSTS file for the pseudo server name/Hamachi IP that does the same, just in case DNS has issues.
Email Application Setup
You should now be ready to launch your email application on the client and point it to the Exchange server. For Outlook, launch it, go to Tools > Email Accounts > Add New > Exchange. Put in the pseudo server name for the exchange server in DNS. It should resolve and allow you to proceed.