mx.worldserver.net has no TXT records.
Question and response
Question
dig mx.worldserver.net. TXT
Answer
The response has no answer records.
Authority
worldserver.net. 1800 SOA coen.ns.cloudflare.com. dns.cloudflare.com. 2394910992 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0