smpt.debitrx.com has no CNAME records.
Question and response
Question
dig smpt.debitrx.com. NS
Answer
The response has no answer records.
Authority
debitrx.com. 2966 SOA ns1.myinfra.fr. hostmaster.cegedim.com. 64645 3600 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0