mail.wisetair.com has no MX records.
Question and response
Question
dig mail.wisetair.com. MX
Answer
mail.wisetair.com. 10800 CNAME traff-https.hugedomains.com.
Authority
wisetair.com. 10800 NS ns1.namebrightdns.com.
wisetair.com. 10800 NS ns2.namebrightdns.com.
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0