extdns01.na.sas.com has no MX records.
Question and response
Question
dig extdns01.na.sas.com. MX
Answer
The response has no answer records.
Authority
sas.com. 600 SOA dns3axxD0101nc0.net.sas.com. dnsadmin.sas.com. 2078288813 1800 300 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0