You'll quickly notice that once you are running a mail server, spam is your main problem. It will account for 60-80% of all messages entering your system and even higher percentages in some cases.

VSMTP32 contains several features that are designed to block spam from being accepted into your system. The main two choices for blocking spam is the DNSBL filter and SpamAssassin.

The DNSBL filter is your first line of defense against spam.

By default, the DNSBL feature is turned off. To turn it on click the Settings menu and choose Relay DB Configuration (DNSBL). Click the Enable checkbox to enable it. The list of domains are the different DNSBL services that it will utilize in the fight against spam. You may add or remove entries as you wish. Generally you want the most effective services at the beginning to save time and resources.

The DNSBL filter is executed when the server receives a new incoming connection. It performs a DNS query on each of the configured DNSBL servers using the incoming connection's IP address. If the result comes back positive then the connection is halted.

There are many DNSBL services available. VSMTP32 is preconfigured with the most popular and most effective. For more information on how this works, try reading the Wikipedia article.

SpamAssassin is an open source program used to detect and filter spam. It is regarded as the most effective spam filter available. It is Perl based and created to run under *nix environments, but it can be compiled to run under Win32. Thanks to the SpamAssassin for Win32 project, it is extremely easy to get this complex program up and running with VSMTP32.

1. Goto https://www.jam-software.com/spamassassin and download SpamAssassin for Windows.
2. Run the installer. You can install it into any directory of your choice. An example could be c:\va\spamassassin.
3. In VSMTP32, click the Settings menu and choose VSMTP32 Configuration. Enable SpamAssassin and set the SpamAssassin directory in the appropriate field.

That is all there is to a basic setup! That of course does not mean that you cannot tweak it further. There are numerous options within SpamAssassin. The SpamAssassin configuration file is /etc/spamassassin/local.cf. For more information visit the SpamAssassin homepage.

One additional step you may want to take is to add the "rewrite_header Subject" value (from local.cf) into your VSMTP32 subject filter. This should not be necessary though.

Note: VSMTP32 versions prior to 2.0 require that you create spamassassin.bat in your VADV directory:

@echo off
c:
cd\va\spamassassin
spamassassin.exe %1 %2 %3 %4 %5 %6 %7 %8 %9
c:
cd\va

You may find that you are still receiving a lot of unwanted mail. You're last choice is to block specific countries that a lot of spam originates from. VSMTP32 makes this very simple. You select which countries to block and if an incoming connection originates from that country, it is dropped. You can search online to find out which countries send out the most spam and determine if this feature is right for you.