Anti-Spam SMTP Proxy Server is a free open-source email client software that enables you to easily implement various automated filtering features on servers. Originally written by John Hanna and now developed by Thomas Eckardt alongside the ASSP community, this productivity program is a platform-independent transparent SMTP proxy server. It’s designed to set up multiple spam filters to help cut down your email-checking time.

Lots of neat tools

The Simple Mail Transfer Protocol (SMTP) is a communication protocol for electronic mail transmission or email. Mail servers and other message transfer agents use SMTP to send and receive mail messages. The original design of SMTP had no capability to authenticate senders or check that servers were authorized to send on their behalf, so email spam and phishing are common issues. This is where Anti-Spam SMTP Proxy Server comes in.

The ASSP is a project that implements a variety of features meant to ward off spam emails. From auto-whitelists to virus scanning, you can really benefit from using this software. Notable features include greylisting, multi-level attachment blocking, blocking reports, multi-level Sender Policy Framework (SPF) validation and blocking, self-learning Bayesian and Hidden Markov Model spam filtering, Penalty Box (PB) trapping, and an automatic crash analyzer.

It also supports various other functions, such as Lightweight Directory Access Protocol (LDAP); plugins for archives, full attachment checking and replacement, and OCR; IPv6 socket; full Unicode; Domain-based Message Authentication, Reporting & Conformance (DMARC); and native SSL for target hosts. To properly install it, however, you’ll be needing some Perl modules first, as this software is Perl-based. The most necessary are Compress::Zlib, Digest::MD5, Net::DNS, and Time::HiRes.

Can be worth the effort

All in all, Anti-Spam SMTP Proxy Server is definitely something email server users should try out. Not only does it offer tons of functions to prevent spam from mixing in with your important emails, but it’s also an open-source project that can easily be modified by anyone tech-savvy. It can be hard to set up, however, especially for beginners who aren’t familiar with its type of interface.