GFI MailEssentials for Exchange/SMTP offers spam protection and email management at server level. GFI MailEssentials offers a fast set-up and a high spam detection rate using Bayesian analysis and other methods - no configuration required, very low false positives through its automatic whitelist, and the ability to automatically adapt to your email environment to constantly tune and improve spam detection. Its advanced Spam detection technology is based on the following key features:
• Bayesian filtering technology (Over 98% capture rate with Bayesian alone!)
• Downloads updates to spam profile database
• Mail header analysis & keyword checking
• 3rd party DNS blacklists (DNSBL) checking
• Foreign language spam blocking
• Automatic whitelist management
• Custom blacklists
GFI MailEssentials also adds key email tools to your mail server: disclaimers, mail monitoring of particular email addresses, centralized mail archiving to database, mail reporting (e.g., top mail users, spam filtering reports etc...), POP3 downloading, auto replies with variables/fields, fake non-delivery reports, seamless integration with Exchange Server 2000/2003 & 5.5 and more!
Freeware Version: GFI provides a freeware version of GFI MailEssentials that includes anti spam and disclaimer features. Using it, administrators can automatically check mail against popular blacklists such as ORDB and SpamHaus as well as add a disclaimer to all outbound mail.
This software is a shareware. You will be able to download and test GFI MailEssentials for Exchange/SMTP during a certain period of time, then, if it does what you need, you will have to acquire the full version from GFI MailEssentials for Exchange/SMTP publisher. The GFI MailEssentials for Exchange/SMTP 11 free trial version contains an installer and an uninstaller, and has a size of 17101 Kilobytes.
For additional information and support request, please contact directly GFI MailEssentials for Exchange/SMTP publisher.

GFI MailEssentials for Exchange/SMTP Screenshot