o1.smtp.vanillaforums.com has no MX records.
Question and response
Question
dig o1.smtp.vanillaforums.com. MX
Answer
The response has no answer records.
Authority
vanillaforums.com. 1800 SOA guss.ns.cloudflare.com. dns.cloudflare.com. 2397122933 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0