GFI MailEssentials for Exchange/SMTP 

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. Also adds key email tools to your mail server.
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netMailshar 

netMailshar is an easy-to-use, powerful mail server that enables every computer in an office to send and receive email not only across the Internet but also within a LAN. It provides centralized, generic protection against all email viruses.
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