ns01.fairisaac.com has no MX records.
Question and response
Question
dig ns01.fairisaac.com. MX
Answer
The response has no answer records.
Authority
fairisaac.com. 300 SOA ns02.fairisaac.com. please_set_email.absolutely.nowhere. 17549 10800 3600 604800 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0