David Bienvenu has announced that the ability to open messages in tabs has been added to Thunderbird in-development code. It’s pretty simple and useful, right-click in a message and select Open Message in New Tab.
As you can see in the screenshot, the folders and messages lists are kept in a separate tab.
It’s still rough in the edges as one may expect from a very early implementation. For example the tab close buttons don’t work and you can’t double click a message to open a tab but this will get worked out in the next few days or weeks along with an option to open message on tabs or windows by default.
Without a doubt a welcomed improvement that Thunderbird 3 users will sure appreciate.