mail06.xinet.com.mx has no TXT records.
Question and response
Question
dig mail06.xinet.com.mx. TXT
Answer
The response has no answer records.
Authority
xinet.com.mx. 180 SOA ns20.digicertdns.com. dns.digicertdns.com. 2009010564 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0