Microsoft Outlook Alternative

Microsoft Outlook is an email client but it also has other features like calender, contact organizer, task manager etc.

http://en.wikipedia.org/wiki/Microsoft_Outlook

Here are few alternatives for this...

Thunderbird

http://www.mozilla.com/en-US/thunderbird/

Pegasus Mail

http://www.pmail.com/

Barca

http://www.pocosystems.com/home/

GMail

http://gmail.com/

Opera

http://www.opera.com/browser/

Zimbra Desktop

http://www.zimbra.com/products/desktop.html

Pimero

http://www.pimero.com/en/

Postbox

http://www.postbox-inc.com/

Spicebird

http://www.spicebird.com/