kaos.verisign.net has no MX records.
Question and response
Question
dig kaos.verisign.net. MX
Answer
The response has no answer records.
Authority
verisign.net. 86400 SOA av1.nstld.com. mdnshelp.verisign.com. 1771892380 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0