mail.dynu.com has no TXT records.
Question and response
Question
dig mail.dynu.com. TXT
Answer
The response has no answer records.
Authority
dynu.com. 3600 SOA ns1.dynu.com. administrator.dynu.com. 76279657 1800 300 86400 1800
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0