Free alternatives for Microsoft Outlook
Outlook is a mail client allowing you to your read and send email by connecting to the server on which your account exists. This is done either by accessing your account via POP (Post Office Protocol) or having Outlook configured as an IMAP (Internet Message Access Protocol) client to retrieve your mail on an IMAP mail server. Among the various free mail clients application you have Phoenix Mail and Thunderbird matching in performance with Outlook express.
PhoenixMail:
Free, open-source email application that can be adjusted for use on different operating systems.
Support multiple mail accounts and provide an easy to use interface.
Thunderbird:
Free, open source email client providing features such as anti spamming filters, and embedded RSS reader.
Support multiple mail accounts and is easily customizable.
http://www.mozilla.com/en-US/thunderbird/