Apache SpamAssassin is an extensible email filter that is used to identify spam. Once identified, the mail can then be optionally tagged as spam for later filtering. It provides a command line tool to perform filtering, a client-server system to filter large volumes of mail, and Mail::SpamAssassin, a set of Perl modules allowing Apache SpamAssassin to be used in a wide variety of email systems.
SubEthaSMTP is an easy to understand Java library that provides a receptive SMTP server component. By plugging this component into your Java application, you can easily receive SMTP mail using a simple abstract Java interface. Also included is a small sub-project called Wiser, an easy to use incoming mail testing framework.
Mireka is a mail server with SMTP, Mail Submission, and POP3 services. It can also be used as an SMTP proxy. As a proxy, it can help to prevent or diagnose mail problems, like outgoing backscatter spam. It provides detailed logging, basic mail traffic statistics, tarpit to prevent email harvesting, and loop detection. It can filter email by DNSBL, SPF, mail size, local domains, and recipients list. Local recipients can be specified using regular expressions. TLS is supported for incoming connections. Aliases, forward lists, and very simple mailing lists can be configured in XML. Custom filters and other components can be written in Java, and they can be easily implemented and installed.
AtMail is a webmail client. The project aims to provide an elegant client for existing IMAP mailservers, with less bloat and a focus on an intuitive, simple user interface. Features include complete Webmail functionality, address-book support, video mail, an AJAX interface, drag'n'drop, and more.
GreenMail is a suite of email servers for testing purposes and sandbox development. It supports SMTP, POP3, and IMAP (including SSL) and can be embedded into any Java application or unit test. The GreenMail Service (SAR) extension runs as a JBoss embedded developer mail server sandbox, manageable via JMX.
PDFassassin is a module for SpamAssassin that allows for the scanning of PDF files in email message attachments. Email bodies are scanned upon connection and checked for PDF attachments. Text is extracted from the PDF via pdftotext and scanned by SpamAssassin. Should the PDF contain images, the gocr program is called to extract the text content. The total spam score of the PDF is compared against the global required_score setting; if it's higher, a score equal to the one specified in pdf.cf is appended to the overall score of the email message.
FuzzyOcr is a plugin for SpamAssassin that can be used on image spam. It supports optical character recognition using different engines and settings, a fuzzy word matching algorithm applied to OCR results, an image hashing system to learn the unique properties of known spam images, dimension, size, and integrity checking of images, and content-type verification for the containing email message.