An excellent question, the answer is "it depends".
The cost of using our service goes up based on the number of email addresses you have. For every email address you have, you consume one credit per month. You can earn credits to keep our service free by placing text link(s) on your webpages to our website.
The value of the link is determined by our proprietary ranking system. A link's credit value is determined by the importance of the webpage where you place the text link. A webpage that receives a lot of traffic has a much higher value than a family photo page that gets only a couple of visitors a month. If you have a webpage that is private, password protected or does not receive any visitors that page would not earn you any credits.
Once you register for our service you will have access to a licensing page where you can enter a website URL, and our systems will evaluate the webpage to determine its value. The higher the importance of the webpage, the more licenses you obtain by placing a link the page.
Most of our clients are able to able to get all their email addresses protected with one or two text links. For users who are not able (or willing) to generate enough credits every month using text links, credits can also be purchased.
We have now deployed mxguarddog for five of our clients and use it on our own exchange server. Out of the box with no configuration it works brilliantly, the quarantine emails are great for the end user.
This system out performs many commercial spam filters we have sold in the past.
We are using MX Guarddog on a few different domains and love it. It has helped tremendously with keeping our time on useful tasks rather than sifting through SPAM.
It seems to just get better and better as well. I can’t say enough about how much we appreciate the service.