Gateway lists are useful when using FortiClient EMS integrated with FortiGate. If using FortiClient EMS without FortiGate, you do not need to use gateway lists.
You can use gateway lists to specify what IP addresses or FQDNs and ports endpoints can use to connect FortiClient Telemetry to FortiGate, FortiClient EMS, or FortiGate and FortiClient EMS. You can create one or more gateway lists and configure them as part of endpoint policies to assign them to domains or workgroups.
After deploying FortiClient to endpoints, FortiClient uses the gateway list to try and connect FortiClient Telemetry to FortiGate or FortiClient EMS. This connection is based on the gateway list that FortiClient received from FortiClient EMS.
Even if the endpoint is already connected to a FortiGate, you can still assign a gateway list to endpoints as part of an endpoint policy. You can also update existing gateway lists as required. The updates are pushed to endpoints with the next Telemetry communication.