mx.o2online.de has no TXT records.
Question and response
Question
dig mx.o2online.de. TXT
Answer
The response has no answer records.
Authority
o2online.de. 600 SOA ns1.o2online.de. domain-de.o2.com. 2026022506 10800 3600 604800 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0