Commercial vs. Free Solutions
In the Windows world, "free" software has often been associated with minimal feature sets, buggy code, and a lack of developer support. In that environment, it's easy to understand why a product costing thousands of dollars up front and thousands more each year for subscription renewals sounds more appealing. Money provides those developers with an incentive to produce better software and to provide support for it.
In some corners of the Unix world, free software is viewed somewhat differently, because the community's experience with such products has been much more positive over the years. Early Unix administrators wrote software to fill whatever needs they encountered, and they shared these solutions with one another, often refining them over time. Because they were exchanging the source code, and not pre-compiled binary versions of their software, other administrators could tinker with the code, adapt it to their needs, and publish their modifications. In the end, these free products gained a reputation for being well-tested and robust. By contrast, closed-source solutions are often met with suspicion in some parts of the Unix world, since it's more difficult to verify the product's robustness, and adapt or integrate the product into existing solutions.
By this point in this long, drawn out discussion we've had over the past five articles, the most flexible and effective tools available for fighting spam at the server level happen to be both free (as in "free beer") and open source. Commercial solutions rarely offer anything that isn't available from tools like SpamAssassin, particularly when combined with a content-filtering framework like amavisd-new, and a quarantine manager like Maia Mailguard. Rather, commercial solutions exist to simplify the process of setting up an integrated spam-fighting solution. However, they come with their own trade-offs: cost, lack of flexibility/adaptability, and in most cases, weak feature sets. Choosing a commercial anti-spam solution tends to mean finding the product that involves the least amount of compromise without shortchanging your organization's needs.
This is not to say that free solutions are perfect. They usually require more effort to install and configure, for one thing, and the documentation can be frustratingly incomplete. Getting things tuned properly requires a bit more patience, along with a willingness to learn more about the underlying issues and technologies than would an out-of-the-box solution.
An administrator with a technical bent can accomplish impressive things with free tools, and it could be argued that having administrators understand E-mail and spam at a more detailed level is something that should be encouraged anyway. Still, if the boss needs a solution up and running tomorrow, a commercial solution may be your best bet.