ns2.peer1.net has no MX records.
Question and response
Question
dig ns2.peer1.net. MX
Answer
The response has no answer records.
Authority
peer1.net. 1800 SOA art.ns.cloudflare.com. dns.cloudflare.com. 2397062560 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0