Communication And Messaging/Email Clients
open source
Nuntius Leo
Nuntius Leo is a free and open source Email client without any advertisements. It is written in c++ with a Qt User Interface. The main function is to provide a very simple email client. It is a personal Email Client like Outlook or Thunderbird. The Lion of the Messages or E-Mail clients might be the right translation of the latin words Nuntius Leo. Or just say: I mail with "Leo". Nuntius Leo.
freeware
eM Client
eM Client is a Windows based e-mail client for sending and receiving e-mails, managing calendars, contacts and tasks. It is being developed as a user friendly alternative to existing e-mail clients and Calendar solutions (MS Outlook, Thunderbird, The Bat). eM Client offers much more than just e-mails and calendars. It integrates Skype functions, RSS feeds and widgets.
open source
Mozilla Thunderbird Portable Edition
Mozilla Thunderbird Portable Edition is the popular Mozilla Thunderbird email client bundled with a PortableApps.com launcher as a portable app, so you can take your email, address book and account settings with you. You can also add in GPG and Enigmail to encrypt and sign your email.
open source
Sylpheed
Sylpheed is an e-mail client and news reader based on GTK+ GUI toolkit, and runs on X Window System.
freeware
Koma-Mail
Koma-Mail is a multilingual, installation-free email client. Runs directly from your USB stick.
freeware
Pegasus Mail
Pegasus Mail is an e-mail client that interacts directly with the user, allowing mail to be sent, read, filed, printed and otherwise manipulated through a graphical interface. Small and fast, it can be left running permanently on the workstation and includes powerful tools to notify the user when new mail arrives. It can run on single Windows computers, or local area networks - it has special support for Novell NetWare LANs that allow it to operate intuitively and with almost no maintenance. It also...
freeware
Windows Live Mail
Windows Live Mail brings together multiple e-mail accounts, calendars, and more into one easy-to-use program. Access and edit your e-mail and calendar events, even when you’re offline, and sync your changes later. Use Windows Live Mail to help maximize your e-mail security across multiple e-mail accounts. Mail combines the ease of use of Outlook Express, with the speed of Windows Live.
freeware
Mozilla Thunderbird
Mozilla Thunderbird is a redesign of the Mozilla mail component. The goal is to produce a cross platform stand alone mail application using the XUL user interface language. The intended customer is someone who uses Mozilla Firefox (or another stand alone browser) as their primary browser and wants a mail client based on mozilla that "plays nice" with the browser.