Defining your Perimeter (Gateway) SMTP Server

The perimeter SMTP server is the Mail server gateway that processes emails received directly from the Internet.

Figure 2 – A typical Perimeter SMTP Relay Server setup

Such gateway SMTP servers are generally specified and configured in the DNS MX records of a domain and are often setup on a De-Militarized Zone (DMZ). The DMZ (see figure above) is a public internal network typically used exclusively for servers that are accessed by external clients on the Internet, such as Web, FTP and Mail servers.

If the inbound emails arriving to the server on which GFI MailEssentials is installed are being relayed from another gateway server, then you must specify your gateway SMTP server details using the Perimeter SMTP Servers tab in the Anti-spam properties in order for the SPF filter and Botnet/Zombie Check features to work correctly. For example, let us take into account a company in England, which receives all its emails on an SMTP server located in the USA. Since the SMTP server in the USA will relay all emails received to the SMTP server in England, the SMTP server in the USA is the perimeter gateway server for the company in England. That is, when the company in England installs GFI MailEssentials on its local SMTP server, they must enable the option in the perimeter SMTP servers page and specify the details of the SMTP server in the USA for the SPF filter and Botnet/Zombie Check features to work correctly.

Screenshot 34 – Perimeter SMTP Server Setup

When GFI MailEssentials is not installed on the perimeter SMTP server, you must:

1. Right click on the Anti-Spam node and select Properties.

2. Click on the Perimeter SMTP Servers tab and enable the This machine is not a perimeter SMTP server option.

3. Click on the Add button and specify the IP address of your perimeter (gateway) SMTP server. Repeat the same process if you want to specify alternative perimeter SMTP servers which you might have available. Please make sure to specify your perimeter SMTP servers in their order of preference, with the actual perimeter server being the one at the top of your list, followed by its alternatives.

NOTE: You can click Automatic discovery to perform a DNS MX lookup to automatically search and retrieve the IP’s of perimeter SMTP servers configured on your inbound email domains.