lightweight email client
Sylpheed Portable can run from a cloud folder, external drive, or local folder without installing into Windows. It's even better with the PortableApps.com Platform for easy installs and automatic updates.
Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client. Sylpheed provides intuitive user-interface. Sylpheed is also designed for keyboard-oriented operation, so Sylpheed can be widely used from beginners to power users. It features support for POP and IMAP, filters, junk mail, and more.