Swift is a library for sending email messages from PHP Web sites and applications. It does not rely on PHP's native mail() function (which is known for using high server resources when sending multiple email messages). Instead, it communicates directly with an SMTP server or an MTA binary to send mail quickly and efficiently. It features custom headers, multiple encoding options, TLS support, embedded images, building and sending multipart messages, fast Cc and Bcc handling, batching messages with or without multiple "To"s, support for multiple attachments, setting message priorities, requesting read receipts, pluggable SMTP Authentication (LOGIN, PLAIN, MD5-CRAM, POP Before SMTP), anti-flooding support (reconnect every X email messages ), secure Socket Layer connections (SSL), and loadable plugin support with event handling features.
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.
vPostMaster is a complete email server for Linux. It is designed to be easily configured in all areas. It includes greylisting, whitelisting, blacklisting, and spam and virus filtering. It supports unlimited domains. It includes Webmail and POP3/IMAP as well as SMTP. Mailing lists and autoresponders are available in the commercial version. It is based on Postfix. The installation uses packages and takes only a few minutes. It features configuration through the Web of all portions of the system from a site-wide policy to per-user preferences and filters.
ACL Policy Daemon communicates with the Postfix MTA using the Policy Delegation Protocol, implementing an ACL (Access Control List) system. Key features: greylisting with flexible storage using memory for fast responses or disk for high persistence, SPF validation, control of messages by day/time, variable message size limits per domain or email, multiple RBL checking, and various ACLs available to use and combine. The configuration is simple and intuitive.
smtpd is a lightweight mail server whose sole purpose is to receive incoming messages and deliver them to local users. Its main "feature" (or non-feature, really) is to be completely unable to relay messages to adjacent servers: if an incoming message is not addressed to a local mailbox, smtpd will reject it. Another convenient feature is its automatic grey-listing of clients that allows you to efficiently reject spammers based on their behaviour. It can handle incoming email traffic for an unlimited number of domains (i.e. act as a MX for these domains) without the need for any configuration (other than creation of users' mailboxes).
The deepOfix Mail Server makes it possible for organizations with minimal technical expertise to have robust server infrastructure. deepOfix offers unprecented ease of use, doesn't require prior GNU/Linux experience and is backed by a full-time development and support team. deepOfix features LDAP-based directory services for user account management, email delivery, distribution lists, and addressbooks. It also includes built in tools for spam and virus control, webmail, and fetching email.
Buni Meldware Communication Suite is an enterprise groupware product providing an email server, calendar server, and a Web mail client. The Web mail portion is written using Adobe's Flash and provides a rich cross-browser experience. Protocol support includes IMAP, POP, SMTP, iCAL, WCAP, and more. It uniquely supports full database email storage as well as file system storage of emails on major database platforms, and is easily installed via a Web Start graphical installation process.