smtp.myworkday.com has no MX records.
Question and response
Question
dig smtp.myworkday.com. MX
Answer
The response has no answer records.
Authority
smtp.myworkday.com. 60 SOA dns1.p01.nsone.net. noc.workday.com. 188 60 60 1209600 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0