Using OpenBSD's spamd as a greylist mail filter
I have an exchange server that doesn’t do a very good job of filtering spam. The server sits inside the firewall/NAT and is reached through port-forwarding. I wanted to stick a device in between the Exchange server and the firewall to filter spam, so I needed a device that would work as a bridge. Spamd works with the pf firewall to redirect smtp traffic that is passing through the bridge to the spamd process. Once a server’s IP address is added to the whitelist by spamd, traffic from that machine passes through the bridge unfiltered. Outbound SMTP traffic is also unfiltered. The users are unaffected because Microsoft Outlook doesn’t use SMTP to inject mail into the server, and so the only thing that should be talking to port 25 (SMTP) should be other mail servers.
For the whole howto click here
Posted by Administrator on Monday, October 09, 2006
