Mozilla Thunderbird is a free, cross-platform email and news client developed by the Mozilla Foundation. The project strategy is modeled after Mozilla Firefox, a project aimed at creating a smaller and faster web browser. Just as Firefox aims to redefine the web browser, Thunderbird is a refinement of the mail and news interface. Users often use them both together.

Thunderbird Features

• Under the Help Menu, you can find the new Migration Assistant to help you set up Thunderbird the way you want it.
• Prior to this new feature you had to know your IMAP, SMTP, SSL/TLS settings. Now all you need to provide is your name, email address, and password and the new email account set up wizard will check our database and find the email settings for you.
• One-click Address Book is a quick and easy way to add people to your address book.
• The new attachment reminder looks for the word attachment (and other words like file types) in the body of your message and reminds you to add an attachment before hitting send.
• The Activity Manager records all the interactions between Thunderbird and your email provider in one place.
• Thunderbird 3.1 changes the way you do email with tabbed email, and a new set of search tools helps you find your emails faster.
• The new Quick Filter Toolbar lets you filter your email faster.
• If you like Firefox's tabbed browsing, you're going to love tabbed email. Tabbed email lets you load emails in separate tabs so you can quickly jump between them.
• If you think you're going to need an email in the future but want it out of your inbox without deleting it, archive it! Archiving helps you manage your inbox and put your email into a new archive folder system.
• Thunderbird is flexible to suit your personality, to give you the features you need, and to fit your work style. Change how Thunderbird looks or add as many features as you want.
• With Personas, lightweight "skins" allow you to change the look and feel of Thunderbird in an instant. Hundreds of skins are available from the latest movies, famous landmarks, and Japanese tattoos.
• Smart Folders helps you manage multiple email accounts by combining special folders like your Inbox, Sent, or Archive folder.
• More information can be found at: http://www.mozillamessaging.com/en-US/thunderbird/features/