I used to have my policy set to reject, but then I found out some part of an Enterprise Outlook mail filtering chain was rewriting the mail I sent before checking the DKIM signature. I can't fix stupid, especially for other parties, so I changed the policy to quarantine instead.

I doubt Russian spammers will care about the difference to be honest. If they accept that their email will be delivered to spam folders, why would they care that the email gets silently dropped? In neither case anyone is going to fall for them.