_spf.mail.lrz.de has no CNAME records.
Question and response
Question
dig _spf.mail.lrz.de. NS
Answer
The response has no answer records.
Authority
mail.lrz.de. 49423 SOA dns1.lrz.de. hostmaster.lrz.de. 2026021022 10800 3600 1814400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0