Picture of Change Mozilla Thunderbird's Start Screen
Just like how you can change the homepage in any web browser,Mozilla Thunderbird also allows you to choose a webpage to show in the message viewing area when it starts.This could be useful,you could make it show a news website and see the news.Then, when you click a link,Mozilla Thunderbird opens the link in your default web browser.

Thunderbird can be obtained from www.mozillamessaging.com/en-US/thunderbird/all.html

Step 1: Open the options menu

Picture of Open the options menu
Go to Tools>Options.It is at the very bottom of the menu.