Open Source C Anti-Spam Software

Open source DKIM library, MTA filter implementation and associated tools.

Mailfilter is a flexible utility for UNIX (-like) operating systems to get rid of unwanted spam mails, before having to go through the trouble of downloading them into the local computer. It offers support for one or many POP accounts.

MailCleaner Open Source Edition is now discontinued but will continue under the spamtagger project https://github.com/SpamTagger [antispam] MailCleaner is an anti-spam / anti-virus filter SMTP gateway with user and admin web interfaces, quarantine, multi-domains, multi-templates, multi-languages. Using Bayes, RBLs, Spamassassin, MailScanner, ClamAV. Based on Debian. Enterprise ready. MailCleaner is an anti spam gateway installed between your mail infrastructure and the Internet. It includes a complete GNU/Linux OS and a graphical web interface for user and administrative access. It comes in the form of virtual machine templates.. - fully compatible with any SMTP mail server (Exchange, Zimbra, O365,...)

Library with anti-spam protect methods, e.g. whitelist, greynet, callback and etc.

SSL Signature Check (SSLSigcheck) is an email filter designed to be run from within procmail. It will examine the signature and certificate of a signed email, and add header information that procmail recipes can use to filter the message.

SpamCheetah is an OpenBSD greylisting based spam filter. It is a liveCD that can run on any machine and it does not modify your hard disk or anything else. It is a network level spam filter and you have to run a separate mail server with it.

XMail anti-spam filters using libantispam.

Is your server running slowly? Clamav-sniffer could help - it scans for malware such as phishes and viruses and configures your firewall to block the cracker.

mod_dnsblacklist is a Lighttpd module that use DNSBL in order to block spam relay via web forms, preventing URL injection, block http DDoS attacks from bots and generally protecting your web service denying access to a known bad IP address.