Hi All,
For some numbers, I have about 40 employees here, and 99% of the mail we receive is SPAM. Right now, it's filtered pretty well by GFi Mail Essentials. In the last 30 days, we received 879,890 e-mails, and 876,999 of those were SPAM. 2,981 valid e-mails out of almost 900,000. On average, I get about 20 pieces of SPAM per minute. A very small percentage of those that got through GFi were still SPAM. No system will be perfect.
I'd like to reduce the amount of work GFi and my Exchange Server have to do by filtering the majority of the SPAM and Viruses before they make it to the internal mail server. I'd like to do this by setting up an OpenBSD Based SPAM/Virus Filter to remove the majority of SPAM and Viruses before forwarding the more valid looking e-mail to my Exchange 2000 Server.
I'm pretty new to OpenBSD. I'd like the system to be locked down as much as possible, and plan to use Packet Filter to only allow mail traffic to and from this server with the exception of SSH for remote administration.
I could use some advice on how to do a secure build specifically for use as a mail relay, and some advice on what software to load to accomplish my objectives. I've heard of ASSP and Spam Assassin, for SPAM filtering and CLAM AV for virus scanning. What do you recommend? Are there other better products out there? I'm looking for free, or inexpensive open source solutions.
I would like the SPAM Filter to be able use multiple options such as keyword blocking, blacklisting, Bayesian filtering, and DNS Blacklists. The solution could use many of those, or just one, but if it uses only one, it should probably be Bayesian.
It should also be easy to whitelist senders.
Thanks for your time and assistance!
Ted
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