Question: Email Spamfilter

I have a question and hopefully someone can help me out here...

Email / calendar are the most used apps on my phone. As a matter a fact: I have about 6x pop-accounts and 1x exchange account running (perfectly) on my SII - Rooted device.

Now I am looking for a good SPAM FILTER for these email accounts. I searched for this, but there is only one solution in the playstore and that costs a lot.

Anyone a solution for this?

Thanks!
G.