mailsenders.netsuite.com has no MX records.
Question and response
Question
dig mailsenders.netsuite.com. MX
Answer
The response has no answer records.
Authority
netsuite.com. 600 SOA a1-124.akam.net. dnsadmin.nsgbu.internal. 2602220130 10800 3600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0