Foxmail is a free lightweight email application that offers you many useful features and a user-friendly interface and supports POP3 accounts, as well as Hotmail accounts, with support for HTML email, mailbox encryption, multiple accounts and more.
Foxmail also comes with a WYSIWYG tool to compose nice-looking HTML emails from templates or scratch. The program also offers filter options, allowing you to act upon incoming mail that meets certain criteria - you can delete messages, forward them, auto-respond to them and more based on keywords appearing in the subject, address, text, etc.
The Express Send feature enables you to send mail directly to the recipient, using the built-in SMTP server, thereby bypassing your ISP.
Foxmail includes many other features, including a remote mail viewer to manage mail on the server, as well as a small scroll ticker that displays message subjects as they arrive in your inbox.
It is probably one of the most capable email programs you can find and an excellent alternative to Outlook Express (can import Outlook messages).