The WaMCom project tries to create versions of Mozilla that are more stable and correct than official Mozilla milestones. In order to achieve that, stable Mozilla releases are extended with backported correctness fixes from the ongoing Mozilla development. In addition, it contains some selected enhancements not yet available in the official Mozilla project, mostly in the areas of security and cryptography. Examples are APOP authentication for POP3 mail, SMTP/SSL, and support for crypto.signText().
Thunderbird is a total redesign of the Mozilla mail component to produce a cross-platform, stand-alone mail application using the XUL user interface language. It has many new features, among them the ability to customize your toolbars the way you want them. a new look and feel with a large number of downloadable themes which alter the appearance of the client, and the ability to add UI extensions.
JPim is an email and contact management tool which offers auto-completion for recipient addresses, viewing of plain and HTML email, viewing of email headers, adding of attachments to email and saving attachments received, full contact management features, an easy to modify quick contact list, and the ability to reply to and forward email.
JEditorCombo is a Java application with a tabbed interface. One tab offers RTF document editing. The other tab offers plain text editing. The plain text editor also offers the ability to send the current document as the body of an email. No additional APIs are required to send the email, since it is handled internally. Both editors have undo and redo capability.
EGroupware is a Web-based groupware suite. It contains many modules, including Calendar (personal calendar and group scheduling, notifications and alarms), Mail (IMAP only), InfoLog (todos, notes, and phone calls linked to contacts/CRM), Contacts (an address book for storing and sharing contact information), ProjectManager, Tracker (bug or incident tracking), TimeSheet, SyncML, CalDAV & CardDAV support, and SiteMgr content management
smtpsend is a simple SMTP client to transmit an email message to an SMTP server. It is designed for use by programs that need a simple, flexible way to send email, or for experimenting with SMTP. In many cases, sendmail can do what this program does, but it is much more complex, harder to set up and use, and doesn't give you as much lower level control. This program is written in Perl and is based on Perl's Net::SMTP module. It makes a great starting point for writing SMTP client functions into your own Perl program.
The AmavisNewSQL SquirrelMail plugin gives you per-user control of a subset of SpamAssassin settings which are stored in a database. It also allows you to use a quarantine database for questionable mail. This plugin was designed with enterprise use in mind, and differs from other plugins in that it works with amavis-new rather than SpamAssassin directly. Most of the code lives in an external class that you can reuse in your own admin tools. It even has support for SOAP calls to perform common tasks.