With such a wealth of high-quality, well-supported anti-spam tools available to Unix administrators at no cost, it probably isn't surprising that there aren't as many commercial solutions available as there are for the Windows server market. The commercial solutions that do exist are generally designed to save administrators the trouble of integrating the various components described in the previous section, by providing all of these in a single, integrated package.
The purpose of such products can be seen as "reducing the complexity" of an anti-spam and -virus solution, and also making a single vendor responsible for supporting the whole set.
Sendmail Mailstream Manager
In addition to the free and open source version of Sendmail that we all know and love (or hate!), a commercially-supported version of this popular mail server is available. The Sendmail Mailstream Manager is an add-on product for this commercial version. It offers virus scanning, spam-filtering, dangerous attachment filtering, and most of the other content-filtering features you'd expect.
With this product, user can control their own filter settings, whitelists, and blacklists from a Web interface (sound familiar?) However, only basic quarantine management is available for end users at this point, with most of the quarantine management features being aimed at the administrator, instead.
Anti-virus vendor Kaspersky offers an anti-spam solution for Linux and FreeBSD users in the form of Kaspersky Anti-Spam, which is designed to integrate with their anti-virus products. As a content filter, it offers a feature recognizer and DNSBL lookups, along with subscription-based updates of new rules to reflect the latest spam patterns.
Quarantine management is not something they've given much thought to, however, though mail can be directed to a user's "junk mail" mailbox.
Proofpoint Protection Server
The Proofpoint Protection Server is another complete content-filtering solution, available for both the Solaris and Red Hat Linux platforms. It combines spam-filtering (DNSBL lookups, feature recognizers, Bayesian learning engine, etc.), virus scanning, and end-user quarantine management facilities for a nicely complete solution.