ns1.my.com has no MX records.
Question and response
Question
dig ns1.my.com. MX
Answer
The response has no answer records.
Authority
my.com. 60 SOA ns.my.com. hostmaster.my.com. 3561859138 60 900 604800 60
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0