mail.secova.de has no TXT records.
Question and response
Question
dig mail.secova.de. TXT
Answer
The response has no answer records.
Authority
secova.de. 900 SOA ns-566.awsdns-06.net. webmaster.secova.de. 1 7200 900 1209600 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0