dns-upper-redirect.xfinity.com has no MX records.
Question and response
Question
dig dns-upper-redirect.xfinity.com. MX
Answer
The response has no answer records.
Authority
xfinity.com. 900 SOA dns101.comcast.net. dnsadmin.comcast.net. 2015042173 7200 3600 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0