mail77.pearsontc.net has no MX records.
Question and response
Question
dig mail77.pearsontc.net. MX
Answer
The response has no answer records.
Authority
pearsontc.net. 900 SOA dns-amer-2.ptns.pearson.com. gns-dnsoperations.pearson.com. 2010121590 900 900 2592000 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0