1. Firstly, you need to log in to your Google Admin Console.
2. Navigate to Apps > G Suite > Gmail > Advanced settings.
3. Under General Settings, select your top-level organization (typically your primary domain) on the left.
4. Scroll down to the Inbound Gateway setting which can be found under the Spam section. Hover over the setting and click the Edit button. This will take you to the Inbound gateway screen.
5. Configure the Inbound gateway using the same settings as below:
A) Gateway IPs
Add the Cyber Security Awareness IP Addresses. For the most up-to-date list of our IP addresses, please see this article.
B) Ensure the Reject all mail not from gateway IPs option is unchecked.
C) Check Require TLS for connections from the email gateways listed above.
D) Message Tagging
Enter "CSAServices" for the Spam Header Tag. This is unlikely to be found in a PST email however this field is required.
E) Select the Disable Gmail spam evaluation on mail from this gateway; only use header value option.
F) Click the SAVE button.