Mozilla Thunderbird 1.0 - A total redesign of the Mozilla mail component.

about:
Mozilla Thunderbird is a total redesign of the Mozilla mail component to
produce a cross-platform, stand-alone mail application using the XUL user
interface language. It has many new features, among them the ability to
customize your toolbars the way you want them. a new look and feel with a
large number of downloadable themes which alter the appearance of the
client, and the ability to add UI extensions.

Changes:
Adaptive junk mail controls, RSS integration, saved search folders, global
inbox support, message grouping, privacy protection, and comprehensive
mail migration from other mail clients.

Release focus: Major feature enhancements
License: Mozilla Public License (MPL)
Project URL: http://freshmeat.net/projects/thunderbird/

Regards
Gordon