Have you tried adding the domains to the Junk email filter? I apologize if this is basic stuff for you and you've already tried it, but right click on an email, select "J
unk" then "Junk E-mail O
ptions..." and then the "Blocked Senders" tab. Add the domain to the list by clicking the "Add..." button:
Also, see my post here
for a bit more on the easiest way to add the domain from an email that you want blocked.