mxrelay1-tor.peer1.net has no MX records.
Question and response
Question
dig mxrelay1-tor.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