This Perl policy daemon is designed for the Postfix MTA and aims to eradicate fake envelope senders and HELOs.
In addition to its powerful features, policyd-weight caches the most frequent client/sender combinations (SPAM as well as HAM) to reduce the number of DNS queries. This prevents your system from overloading when trying to score and verify multiple DNSBLs, DNS records and client/sender combinations.
Policyd-weight is designed to work after the first three SMTP commands (HELO, MAIL FROM:, and RCPT TO:). It allows you to verify and score the client's IP address, corresponding DNS records (A, MX and PTR), and multiple DNSBLs. If the client tries to forge headers or supplies non-existent DNS or bogus data, the spam score will increase. This allows you to reject such mails while in transfer, before the mail body is received by your MTA.
Compared to SpamAssassin or amavisd-new, filtering or scoring with policyd-weight is different. With policyd-weight, mail is not accepted/queued, and less CPU-time is wasted, less bandwidth is used, and mail cannot be rejected without creating a bounce.
Postfix' built-in checks can be too tough for poorly configured clients. One hit, and the mail gets rejected. Policyd-weight is designed to be fair, thus allowing DynDNS MX users to get through if their MTA is set up correctly, even if their ISP net is DUL-listed. This is because its decision whether to reject or accept a mail is based on multiple factors.
While policyd-weight is great by itself, you can also run it with other programs, such as SpamAssassin and Clamav, further decreasing the need for bandwidth and CPU cycles. Also, you might not need greylisting, SPF, extraordinary whitelists or SQL and other DBs anymore. This makes policyd-weight an essential tool for anyone looking to improve their system's spam and virus mail blocking capabilities.
Version 0.1.14 Beta 17: N/A