Inbound gateway

In some cases, your business might be using an inbound mail gateway for the prefiltering, archiving, or preprocessing of incoming messages. In this case, you need to set up an inbound mail gateway. To do this, hover your cursor over the Inbound gateway section and click CONFIGURE, which will appear on the right-hand side, to open the Add setting | Inbound gateway form:

First, write a short description for this gateway. This will help as a quick reference in the General Settings | Inbound gateway summary:

Then, write the IP address, or range, for this server and choose whether you wish to activate any of the following options:

• Automatically detect external IP will make Gmail verify whether an email is emanating from the external IP of a whitelisted server
• Reject all mail not from gateway IPs will reject anything that is not coming from your inbound gateway to make sure that nothing is bypassing it
• Require TLS for connections from email gateways is a standard that uses Secure Socket Layer (SSL) encryption technology that helps to prevent attackers from intercepting the message during transportation

We can set up custom spam filtering criteria by enabling the Message Tagging option that allows users to define custom spam filters using regular expressions (regex), either by matching text patterns, complete words, text with variable characters, or even scoring the contents to see how similar they are to a regex and set a threshold based on that score. We will talk more about filtering things by content when we talk about setting up Objectionable content in the Compliance section.

If we want to rely solely on our inbound gateway's security, we can disable Gmail spam evaluation for content coming from this gateway. In this case, Gmail will only use the header's information for potentially suspicious inbound messages.

Once you are finished setting up the new inbound gateway, click ADD SETTING to return to Settings for Gmail | Advanced Settings.