mx1.lightower.com has no CNAME records.
Question and response
Question
dig mx1.lightower.com. NS
Answer
The response has no answer records.
Authority
lightower.com. 251 SOA mrbodnsmaster101.nss.crowncastle.com. hostadmin.crowncastle.com. 2020040028 10800 3600 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0