[...] Thunderbird, the free email, chat and news client
it first developed in 2004 [...]
In 2004 Thunderbird spun off the Mozilla Suite (Browser, Mail, WYSIWYG HTML editor, IRC-chat client), like Firefox.
And Mozilla Suite is based itself on Netscape Suite, that AOL donated as open source code and formed the Mozilla Foundation (Mozilla was the internal codename of Netscape).
The Netscape Suite was a complete rewrite of Netscape Navigator 4. That long rewrite phase and the choosen technology (XUL, XPCOM, etc) contributed to loosing the Browser war agaist IE 5/6.
Thunderbird barely changed since 2004. Back then it was a direct competitor to Outlook Express.
And Mozilla Suite is based itself on Netscape Suite, that AOL donated as open source code and formed the Mozilla Foundation (Mozilla was the internal codename of Netscape).
The Netscape Suite was a complete rewrite of Netscape Navigator 4. That long rewrite phase and the choosen technology (XUL, XPCOM, etc) contributed to loosing the Browser war agaist IE 5/6.
Thunderbird barely changed since 2004. Back then it was a direct competitor to Outlook Express.