DavMail is a POP/IMAP/SMTP/Caldav/Carddav/LDAP exchange gateway allowing users to use any email/calendar client (e.g. Thunderbird with Lightning or Apple iCal) with an Exchange server, even from the Internet or behind a firewall through Outlook Web Access. DavMail now includes an LDAP gateway to Exchange global address book and user personal contacts to allow recipient address completion in the mail compose window, and full calendar support with attendees free/busy display.
openICEM is a highly scalable server software that aims to provide a certified email service as specified by Italian law. It is based around the Postfix MTA, python-ldap, and python-clamd. It makes use of XML-RPC for communication among servers and does not require any shared service or shared filesystem.
Inbucket is an email testing service. It accepts messages for any email address and makes them available to view via a Web interface. It allows Web developers, software engineers, and system administrators to quickly see the emailed output of their applications. No per-account setup is required. Mailboxes are created on the fly as mail is received for them, and no password is required to browse the content of the mailboxes.
S22.Imap is an easy-to-use and well-documented .NET library component for communicating with and receiving electronic mail from an Internet Message Access Protocol (IMAP) servers. It supports IMAP IDLE notifications and IMAP over SSL, allows selective fetching of parts of mail messages, is inherently thread-safe, and is well documented with lots of example code.
Sendooway is a multi-user and multi-target ESMTP proxy that acts as mail transfer agent. Instead of configuring SMTP servers and authentication data for every mail identity on every device, it allows you to configure them centrally. Sendooway automatically uses the correct smarthost, logs on with the user's account data, and sends their mail.
Exim4U is a Web-based user interface and integrated software configuration for the Exim message transfer agent (MTA). Using any modern Web browser, you can use it to manage Exim email domains, user accounts, aliases, forwarders, and much more. Exim4U is a derivative work of the Virtual Exim (Vexim) project.
WAWAS is a full PHP application server. The main server core listens to any IP/port and passes data to any mounted protocol on the listener. Implemented protocols are HTTP1.1/1.0, Comet, Telnet, DNS, mail, and FTP. Each protocol runs modules that build response data based on the requests. Memory object persistence allows data and caches to be shared across protocols or time. All configuration uses XML. It can be launched as a daemon, with or without forked workers, and is nearly as fast as Apache in preliminary tests.
OpenSMTPD is an RFC compliant, secure, and simple SMTP server ported from OpenBSD to Linux. It supports the SMTP protocol, including SSL versions for added security, virtual domains, forward files, and external delivery agents like procmail, and can do most of the basic things that other MTA implementations do.
claws-mail-indicator is a simple plug-in which adds support to Claws Mail for the Ubuntu indicators. Notifications are displayed in the Messaging menu, with the option to display a notification bubble each time new messages arrive. It was developed and tested on Ubuntu 11.04 (Natty) 64-bit.