ns1.verizon.net has no MX records.
Question and response
Question
dig ns1.verizon.net. MX
Answer
The response has no answer records.
Authority
verizon.net. 86400 SOA ns1.verizon.net. dns.verizon.com. 2025091501 86400 3600 15780000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0