filter.cyso.net has no TXT records.
Question and response
Question
dig filter.cyso.net. TXT
Answer
The response has no answer records.
Authority
cyso.net. 300 SOA ns1.cyso.nl. dnsadmin.cysonet.com. 1772616158 16384 2048 1209600 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0