Issue Mail: dmarc-Problem

[KlausZ]

Hello,

we have Plesk 17.5.3 Update 55 on a centos 7.5.1804 Server an a problem with incoming mails.
We have checked the dmarc-Check for incoming mails. So from some persons the mail wouldnt received to the mailbox and in the maillog you will see:

Sep 6 15:59:32 xxx dk_check[56435]: Starting the dk_check filter...
Sep 6 15:59:32 xxx dk_check[56435]: DKIM verify result: DKIM verification (d=test.de, 32767-bit key) failed: key DNS query failed
Sep 6 15:59:32 xxx dmarc[56436]: Starting the dmarc filter...
Sep 6 15:59:32 xxx dmarc[56436]: Wrong the essential DMARC policy parameters for test.de.
Sep 6 15:59:32 xxx dmarc[56436]: DMARC: REJECT message for [email protected]
Sep 6 15:59:32 xxx postfix-local[56396]: message discarded by a mail handler

Any suggestions?
Thanks a lot.

Bye