mx1.pasty.com has no CNAME records.
Question and response
Question
dig mx1.pasty.com. NS
Answer
The response has no answer records.
Authority
pasty.com. 2446 SOA ns1.pasty.net. hostmaster.pasty.net. 2025111600 28800 7200 1604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0