mxN.pulsesmtp.com has no CNAME records.
Question and response
Question
dig mxN.pulsesmtp.com. NS
Answer
The response has no answer records.
Authority
pulsesmtp.com. 10111 SOA a.dns.gandi.net. hostmaster.gandi.net. 1768125027 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0