mail4.springleaf.com has no CNAME records.
Question and response
Question
dig mail4.springleaf.com. NS
Answer
The response has no answer records.
Authority
springleaf.com. 10608 SOA ns1.markmonitor.com. hostmaster.markmonitor.com. 2025081501 86400 3600 2592000 172800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0