MailTabs for Mail.app
MailTabs for Mail.app is a unique plug-in that organizes all your open email messages under a simple tab arrangement just like the tabs in your browser.
Mail.app is great for email and comes free with every Mac. However, like many email applications, it doesn't take long before you have lots of mail windows open and before you know it, your desktop is cluttered with messages. Tabs have revolutionized the way we browse multiple web pages, now they are doing the same for email.
MailTabs for Mail.app can be downloaded at tabs4mail.com. You will be redirected there shortly.