That there's need for such a utility is obvious. At $US 30 per seat for Outlook and a shameful Deersoft (the commercial Windows Spamassassin
Last I looked (few months back), Exchange licenses cost $63 US each. If you really needed it for an organization, you could setup a mail server with postfix or sendmail, to filter out the spam, and then just relay it to an internal Exchange server. Cost is minimal (use some leftover hardware). I'm thinking of doing just that with my Exchange server at work.
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