FortiMail config-only HA with centralized tracking,quarantine and policy configuration

We need to configure HA between two FortiMail appliances, one in HQ and other in DR. Each of the nodes will have IP address from different IP subnet ( for example 192.168.10.1 and 192.168.20.1) since the MPLS link is a L3 link. So I believe that the customer should go for Config-Only HA mode since Active-Passive needs the nodes to be on the same IP subnet (for example 192.168.10.1 and 192.168.10.2). The customer wants to track emails, configure policies and the quarantine access to be on a single box. Is this really possible with config-only HA?.