ns2.heliohost.org has no MX records.
Question and response
Question
dig ns2.heliohost.org. MX
Answer
The response has no answer records.
Authority
heliohost.org. 86400 SOA ns1.heliohost.org. heliohost2.gmail.com. 2021061803 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0