smtp.bitnet.pro has no MX records.
Question and response
Question
dig smtp.bitnet.pro. MX
Answer
The response has no answer records.
Authority
bitnet.pro. 1800 SOA jaziel.ns.cloudflare.com. dns.cloudflare.com. 2397084643 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0