I can see why he would want to do that - 99% of the spam I get is from US-based cable modem- and DSL-hosted systems. My host - earthlink - recently reconfigured their routers to disallow outbound email that doesn't go through their servers, and I wish all ISPs would do that.
Perhaps . . . but I've been getting relayed spam trough XO's legitimate SMTP servers for a few years now. Using the ISP doesn't exactly solve or possibly even reduce the problem.
