If the user doesn't use tabs, then the folderpane header should not be a tab. For non-tab users, the entire tab toolbar is a huge waste that's further damaging to usability because the desktop peeks through and makes getting to other toolbar items that much harder.

The initial argument to show just a single tab by default as well when tabbed mail was introduced was to advertise that new feature, which could be argued is no longer necessary now that it's established. Another reason was added with the quick-filter bar, where the toggle for showing or hiding it is tied to the tab bar (i.e., that handle becomes invisible when hiding the bar for a single tab). It can be hidden with mail.tabs.autoHide, but there is no UI yet (bug 533930).

(In reply to comment #1) > Another reason was > added with the quick-filter bar, where the toggle for showing or hiding it > is tied to the tab bar (i.e., that handle becomes invisible when hiding the > bar for a single tab). Really, it shouldn't be there in the first place.

Dão, I agree that this wasn't a good choice for exactly that reason, but the quick-filter bar handle ended up where it is right now, thus for the time being this has to be taken into consideration when talking about the tab bar...

I'm pretty sure that the Lightning extension requires a tab bar as well. In other words, if you use lightning, you must have a tab bar.

(In reply to comment #4) > I'm pretty sure that the Lightning extension requires a tab bar as well. > In other words, if you use lightning, you must have a tab bar. Lightning has buttons you can put on the toolbar.

(In reply to comment #5) > (In reply to comment #4) > > I'm pretty sure that the Lightning extension requires a tab bar as well. > > In other words, if you use lightning, you must have a tab bar. > > Lightning has buttons you can put on the toolbar. Filed as bug 673990

With tabs in titlebar the tabs uses less space and I daresay the users are now familiar with tabs to leave then always visible. FX has completely disabled the ability to hide the tabs. For them which still wants remove the single tab can still use the mail.tabs.autoHide pref. With Win8 and 10 where is also no background which can peek through.