NoGlass is a free theme promising it will remove Aero glass in Thunderbird, giving also the option of colored icons. The theme removes only the Aero glass areas at the toolbars adding basic ::More

Nautipolis is a free theme for Thunderbird, with icons based on art gnome. Thunderbird 5 tries to become more aero-like for Windows, introducing a default theme that features large transparent ::More

You may face this problem with Thunderbird 5, a status bar that shows at the left bottom corner, only how many messages are unread – no information at all when you connect to your mail ::More

Normally in Thunderbird when you write, paste or select an email address at the recipient’s editing box (To:), then pressing the Enter button, this address is kept while the cursor moves to ::More

I think Internet Explorer introduced Full Screen mode and now all major browsers support it. Not all email programs though. Thunderbird won’t give anything better than a maximized mode, and ::More