dns2.upcloud.com has no MX records.
Question and response
Question
dig dns2.upcloud.com. MX
Answer
The response has no answer records.
Authority
upcloud.com. 1800 SOA dns1.upcloud.com. dns.cloudflare.com. 2396888040 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0