Launch browser from Thunderbird
From MozillaZine Knowledge Base
Thunderbird doesn't provide a built-in browser, if you want a combination of a email client and a browser the best solution is to use SeaMonkey instead.
A relatively unknown feature in Thunderbird was the ability to click on the throbber and launch Firefox. That was deliberately removed in version 2.0. The Mr. Techs Local Install extension restores that feature.
The ThunderBrowse extension adds a browser to the Thunderbird message preview pane. Besides viewing web pages in it, you can right click on a link in a web page and view that web page using your system's default browser.
The URL Link extension lets you open a link using your systems default browser. It also knows how to reconnect links that have been broken across several lines, and to replaces spaces with the URL character code %20 in order to use e-mailed network 'file:' links.
The Launchy extension lets you open links using external applications such as IE, Opera, Mozilla, Outlook, BSPlayer, and Windows Media Player. Right click on a link in a mail message and choose "Launchy". It also supports a custom toolbar button but that seems to have problems specifying the messages location with Thunderbird 2.0