iRULE to allow active sync access only for certain geolocation

You can try this:

when CLIENT_ACCEPTED {

    set allowed 0

    if {  [whereis [IP::client_addr] country] eq "SG" } {

        set allowed 1 

    }

}

when HTTP_REQUEST {

    if { [HTTP::path] starts_with "/microsoft-server-activesync"  and $allowed == 0 } {

        HTTP::respond 403 content "Active Sync is blocked"

    }

}