The next version of Thunderbird has been in the works for more than a year now and has just reached beta stage.

This is what’s new in this beta.

• Message Tags
• Folder Views
• Visual Identity Improvements (theme improvements for Windows and Linux)
• New Mail Notification Alert Improvements
• Session History Navigation (back / forwards)
• Find As You Type in the message pane
• Automatic detection of online state (Thunderbird can automatically move you to offline mode when you lose net connectivity)
• New Windows installer based on Nullsoft Scriptable Install System
• Updates to the extension system
• Extensions can now add custom columns to the thread pane and store custom fields in the mail database.
• New combined and improved Add-ons manager for extensions and themes
• Preference dialog redesign
• Remote image policy changes
• Support for editing tags
• Ability to customize the fields we show in the new mail alert notification
• Recent folder menus for Copying and Moving messages.
• Two pane view using a folder location picker toolbar widget.
• Universal Binaries for Mac OS X builds.