|For my money, I would have to suggest any of the Barracuda spam filter products. They are costly, but well worth it. All of the clients where we have installed these have seen a 95%-98% reduction in the amount of spam that gets through. |
Depending on the number of users you have, this might be a more cost effective solution as it is a central appliance and can filter for the entire domain or even multiple domains.
They also offer a 30 day free trial so you can see if it would be worth it for your particular situation.
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