outbound.telmex.com has no TXT records.
Question and response
Question
dig outbound.telmex.com. TXT
Answer
The response has no answer records.
Authority
telmex.com. 300 SOA ns8.telmex.com. dominios.telmex.com. 657241153 10800 3600 604800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0