What about a 30-day trial period - where you chaps send a report to the trial user detailing all the spam you've blocked during the trial.

In this way, we can see if it's value for money, and in all likelihood, take up the paid subscription.

I think this is a very valuable service and I will suggest it to my bigger clients... but many Zenners are "garden-shed retailers" who may find even $9 a bit steep!

(I hasten to add, I'm not one of them! )