Firstly, you can't stop the spam, now you are on the lists all you can do is deal with it when it comes in.
First thought.... do what the support guys have told you to do and disable the rule that is causing the problem, you don't have to delete the rule, you can just switch it off to see if it helps, if it doesn't then switch it back on again.
You can also set outlook to automatically clear the deleted items on exit if you don't like having to do it manually.