webmail2.cotas.com has no CNAME records.
Question and response
Question
dig webmail2.cotas.com. NS
Answer
The response has no answer records.
Authority
cotas.com. 3009 SOA calleja.cotas.com. gmorenoc.cotas.com. 2018031053 1800 900 1296000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0