Disable tabs in Mozilla Thunderbird

If you want to save a little space, consider disabling the tab area. By default it's only used to show the current folder.

To disable tabs, open Edit > Preferences:

1. Set "Open messages in:" to "A new message window"
2. Click "Config Editor" button at the bottom, and double-click mail.tabs.autoHide, to set it to true

However, if you search or open Tools > Add-ons will be displayed in a tab regardless.

Default, with tabs

With tabs disabled

For more, see:
https://www.ghacks.net/2014/12/09/how-to-turn-off-tabs-in-mozilla-thunderbird/
http://forums.mozillazine.org/viewtopic.php?f=39&t=2093003