SAwin32 is a POP3 proxy that includes SAproxy graphical user interface and SpamAssassin engine. This spam filter stands Between your email reader and the POP3 (incoming) Mail Server. It can study the message and check whether it matches patterns common for spam; contact online "blacklists" (DNSBL) to verify whether the message has arrived from a known spam source; contact online databases DCC and Razor (Cloudmark) which collect the "Fingerprints" of millions of known spam messages; automatically learn how to tell spam from non-spam (statistical analysis); automatically whitelist frequent senders; easily configure basic settings with the help of a user-friendly interface; support custom rules (although that requires reading SpamAssassin documentation).
The result is very high precision of email classification: the filter properly identifies and marks nearly all spam messages, while the false positive rate, that is, the amount of incorrectly classified legitimate mail, is virtually zero.
SAwin32 supports SSL and works with any email client (Outlook, Eudora, etc.), but only with POP3 mail accounts. Thus, it will not work with web-based email (such as Hotmail), IMAP, Microsoft Exchange, Lotus Notes, etc. In order to use this filter, you need to know the name of your POP3 (incoming) mail server. It typically looks like pop.isp.tld. You can find it in the configuration of your email client or by asking your Internet Service Provider.
The history of the filter started in 2002, when Dan McDonald successfully ported SpamAssassin to Microsoft Windows by writing pop3proxy Perl script that was acting as a proxy between the mail client and the POP3 server. Further work on this script lead to the release of the free spam filter SAproxy and then commercial SAproxy Pro. Soon after the release in 2003, Consumer Reports declared SAproxy the best personal anti-spam solution for Windows.