mx.colt.net has no TXT records.
Question and response
Question
dig mx.colt.net. TXT
Answer
The response has no answer records.
Authority
mx.colt.net. 300 SOA mc27.lon.server.colt.net. hostmaster.colt.net. 2009100700 1800 1200 3600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0