Windows Server 2012 Essentials is different from previous versions of SBS as it’s designed to work with 3 different types mail systems. As a result the ports you need to have open on your firewall is also different.
If you have a uPnP router then the configuration wizards in Windows Server 2012 Essentials will do the work for you. If you like me elect to disable uPnP then you will need to configure the firewall port forwarding manually.
Here’s the list of ports you need to open on your firewall for Windows Server 2012 Essentials. Note that not ALL of them need to be open in order for things to work.
Port 25 – is NOT required to be open if you are using a cloud based mail system such as Office 365 then this port can and should be closed. ONLY if you have an onpremise Exchange or other mail server should you open this port to your network. If you have an onpremise Exchange or other mail server, then you will port forward this port to that server and not the Windows Server 2012 Essentials server. If you have no external email filtering or antispam software then you will need to leave this open for all external IPs. If however you are using something like ExchangeDefender or Trend IMHS then you will need to lock down the external IPs that this port can talk to.
Port 80 – does NOT need to be open at all in reality. It’s there to provide an easy redirect for our users when they go to access the Anywhere Access feature of Windows Server 2012 Essentials (formerly known as Remote Web Access). Having this port open allows the user to type in remote.mycompany.com into a web browser which will then go direct to our server. The server will immediately redirect the user to https://remote.mycompany.com/remote so that all traffic is encrypted. You can safely close this port to reduce your attack profile but you will need to train your users to type in the full URL of https://remote.mycompany.com/remote. My advice is to train your users – put this URL on the back of a business card for them to make it easy to handle.
Port 443 – this is a mandatory one. This needs to be open and forwarded to your Windows Server 2012 Essentials server to allow access to the Anywhere Access website. All traffic over this connection is encrypted so it’s safe and secure. If this is not open then none of these functions will work outside your office. This port is also used by default for the SSTP VPN protocol which is the default protocol in Windows Server 2012 Essentials.
Port 1723 – is an optional port on Windows Server 2012 Essentials. You see – the default protocol for VPN is now SSTP which runs over port 443. You will only need to open port 1723 if you have client PCs that can not use SSTP to access your server. Make sure if you have a more advanced router to also allow the GRE protocol (type 47) over this port.