If you want to outsource the entire problem, try a service like Sprint's "SEPS", which costs $250/month, and works very well. 97% of e-mail to our domain is spam, and SEPS handles it correctly to at least 4 9's.
All admin is via web browser and, although it's sometimes slow, it's pretty straightforward. Set up a reject list, put your valid users on it, and save SPAM for a day or so, just in case. Then, you simply point your DNS for incoming mail to SEPS IP address, and collect your mail internally from their mail server instead of yours.
A side advantage is that, if your MTA goes down, or you lose Internet service, etc., SEPS queues the mail up for you, and delivers it when you come back online.
If you can spend $3000 a year, it's one less headache and worth the cost, IMHO.
http://www.sprint.com/business/products/products/spamFiltering_tabA.html or thereabouts, to get started.
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If you want to outsource the entire problem, try a service like Sprint's "SEPS", which costs $250/month, and works very well. 97% of e-mail to our domain is spam, and SEPS handles it correctly to at least 4 9's. All admin is via web browser and, although it's sometimes slow, it's pretty straightforward. Set up a reject list, put your valid users on it, and save SPAM for a day or so, just in case. Then, you simply point your DNS for incoming mail to SEPS IP address, and collect your mail internally from their mail server instead of yours. A side advantage is that, if your MTA goes down, or you lose Internet service, etc., SEPS queues the mail up for you, and delivers it when you come back online. If you can spend $3000 a year, it's one less headache and worth the cost, IMHO. http://www.sprint.com/business/products/products/spamFiltering_tabA.html or thereabouts, to get started.