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I have finally implemented the spam software Xeams as a front end to SmarterMail running on the same computer. Xeams is a totally free spam engine with features far superior to SmarterMail spam detection. The live logging is what got my attention. This is not a sales pitch, this product is totally free.
Here are the steps to add it to SmarterMail
Assumptions for the examples below (substitue your IP's)
You only have 1 public IP address. The address is 126.96.36.199. MX record for your domain refers to this address.
The internal IP address of your primary server 192.168.20.2
Your firewall forwards in-coming traffic for port 25 to 192.168.20.2
You have a working SmarterMail server and want to add a superior spam filter.
Modifications to computer/server
Add IP address 192.168.20.3 to WAN NIC IPv4 in TCP settings
Modify the SMTP port used in SmarterMail from 25 to 2525. Settings>Bindings>Ports
Configure SmarterMail to forward all out-bound messages to 192.168.20.3. Settings>Protocol Settings>SMTP out.
Insure Domains>Edit>Technical>Outbound IPv4 is set to 192.168.20.3 for every domain.
Xeams Installation Procedure
Install Xeams for Windows on the machine.
Configure Xeams to run in Firewall mode. Server Configuration. Add DNS Servers
Enable SMTP Proxy Server, bind to 192.168.20.2, SMTP Proxy port 25, Actual Email Server Host 192.168.20.2, and Actual Email Server port 2525.
Enable SMTP Server, bind to 192.168.20.3, SMTP port 25.
Add the IP 192.168.20.* in Relaying tab, set for closed relay, Reject emails for invalid users-off (unless user list is added).
Add all local and client IP's to whitelist. ie 192.168.1.*
Have at least 4GB memory and increase Max Memory to 1/2 free/available memory. Home>Memory Status>settings. Follow directions for reinstalling Xeams service
Running the SMTP Proxy only did not work for me with SmarterMail because of port conflicts. You must run the SMTP Server as well.
After a solid testing period, disable all the spam filters in SmarterMail to increase performance.
Add ClamAV after a solid testing period.
Tested on an HP Pro 6300 with i3-3570, 8GB, 500GB HD, Windows 7. Running now on a Dell T20 Server, Xeon E3-1280, 16GB, 500GB SSD, Windows Server 2012 R2
Ensure you do not have any SMTP blocking enabled in Security>Advanced Settings>Abuse Detection. This will cause the Xeams server to be blacklisted if a brute force or similar attack happens.