Running a traceroute from a place that does have reachability to your mx vs the traceroute from the guys who cannot could identify if they are being blocked early or near the last hop towards your network. Usually the final hops towards your own router are always the same so you should at least see if they reach the hop right before your MX barring the ISP sends ICMP ttl expire messages back to you of course 🙂 ... View more