domain names, for example clintonemail.com or cometpingpong.com resolve to IP addresses (or are aliased to other hostnames) - these are called A records. MX records essentially tell mail servers where incoming email is supposed to go (so for example, if you email [email protected], the MX record is what figures out where that message ultimately gets routed to). Collectively, these types of records are called DNS records. It appears that many people think there is overlap between the DNS records of cometpingpong.com, wethepizza.com, and clintonemail.com. If true, this would indicate that those domains are hosted by the same web space provider, or operated by the same server administrator(s). Also, if any of this information changed at times surrounding when indictments were issued, that would be mighty suspicious.