I looked into it and yes you're call center chap is spot on. But most mail servers do not come configured to receive mail on that port and have to be set to allow it and the firewall admin, (could be the same chap), would have to open the port on the firewall so that any external IP can reach that port on the mail server. But yes, it's all very viable. Who on earth did you call that had a call center wallah that well informed????
