Yes I did that already, see here 
Support wanted on DNS host name records
Just to make shure:
The spam-server of mycompany.com works completly different. It is a provider, Retarus, who manages the mail system. If a incommoing email is considered as spam, it is not delifered to the recepient at all. Instead of delivery the recipient (in this case thorsten.lastname@mycompany.com) recieves an email from Retarus with a table of suspectious e-mails as hyperlinks. I need to request each of such emails individually. Upon selection request retarus sends the original email to the intended recipient.
In short words: Imagine rspamd would hold / delay suspectious mail until an release notification is responded. It would put such released mail to the inbox without any change of header.
I this case, the retarus spam system does not consider the mail from the OKI printer as spam as it was relayed from the valid nethserver.