sb.west.net has no MX records.
Question and response
Question
dig sb.west.net. MX
Answer
The response has no answer records.
Authority
sb.west.net. 1800 SOA jo.ns.cloudflare.com. dns.cloudflare.com. 2396256473 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0