Deployment option A: Installing Mail essentials on a separate machine (Inbound & Outbound security) A good deployment option is to install Mail essentials on a separate machine in front of your firewall. This allows you to keep your corporate mail server behind the firewall. Mail essentials will act as a smart host/mail relay server in the perimeter network (also known as DMZ, demilitarized zone, and screened subnet). Additional advantages are: You can perform maintenance on your Mail server machine, whilst still receiving email from the internet. You use less resources on your Mail server machine The Mail essentials machine can have a lower spec then the Mail server machine and process mail faster Additional fault tolerance – if anything happens with your Mail server you still receive mail, which is queued on the Mail essentials machine. Note: This separate machine does not need to be dedicated to Mail essentials, it can be running other applications. If you choose this option, you have to configure IIS5 before installing Mail essentials. Go to the paragraph 'installing Mail essentials on a separate machine' for instructions how to do this.