Reject emails coming from specified domains

Hello,

Is it possible to reject all emails coming from specified list of domains?

IMPORTANT: I don’t want to mark it as spam, I want to reject all of them.

If not acceptable to block the domain in spamassassin ‘address deny’, then…

Find the IP of the mail server for the domain and block it at the firewall. Either completely or just for incoming mail ports on that IP. Only issue is, the Ip can change and you wouldn’t know it without setting up a dns check of your own.