smtp1.uservoice.com has no MX records.
Question and response
Question
dig smtp1.uservoice.com. MX
Answer
The response has no answer records.
Authority
uservoice.com. 1800 SOA ns1.uservoice.com. dns.cloudflare.com. 2394820613 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0