Blocking specific domains from reaching Apple Mail inbox

I suspect an ex-employer is signing me up for all sorts of hateful emails and I am receiving them in my Apple Mail inbox. I've set them to go to my trash and marked as spam as well as blocking them - but blocking doesn't stop them from coming in to my email - I have to check my spam and trash folders to be sure no legit emails got in there (as they sometimes do) so i see these emails. Is there no way to block these domains from ever reaching my inbox? I've tried Spamsieve, but that won't do what I need.

[Re-Titled by Moderator]

Original Title: Is there any way to block certain domains that email my Apple Mail email addresses from reaching my inbox?