I'd be delighted to hear all this stuff is built into modern versions of Exchange.
Our Exchange server is rather old (2005) and we're getting ready to upgrade.
#GFI MAILESSENTIALS GREYLISTING WINDOWS#
In particular, it is acceptable for the filter to run on either Windows or Linux.
Since such a filter accepts SMTP messages on a publicly visible SMTP port, and forwards (filtered) messages to an internal SMTP port that we provide for Exchange, it doesn't matter where it runs to us. Other features such as Bayesian learning are nice to haves but not necessary.
The ability to eliminate (spam) email by checking for certain string patterns using some simple wild string matches (text with asterisks for wildcards).Graylisting (simply ignoring a first email from sites previously unseen real mailers at such sites resend after a bit so such mail gets through, but spammers almost never resend).1% of 10K spam messages per day is still really a pain. Spam is a constant problem we get thousands of spam messages a day and manage to remove most of the spam by using a filter on our incoming SMTP port. We operate a small Windows shop with Exchange.