mx2.cs.getresponse.com has no CNAME records.
Question and response
Question
dig mx2.cs.getresponse.com. NS
Answer
The response has no answer records.
Authority
getresponse.com. 110 SOA ns0.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2020014253 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0