mx01.kundenserver.de has no TXT records.
Question and response
Question
dig mx01.kundenserver.de. TXT
Answer
The response has no answer records.
Authority
kundenserver.de. 600 SOA rns.ui-dns.de. dnsadmin.1und1.de. 2013099672 10800 3600 604800 600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0