mailstream-west.mxrecord.io has no AAAA records.
Question and response
Question
dig mailstream-west.mxrecord.io. AAAA
Answer
The response has no answer records.
Authority
mxrecord.io. 5 SOA poppy.ns.cloudflare.com. dns.cloudflare.com. 2395354140 10000 2400 604800 5
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0