Don't open all mails when double-clicking at sorted group headings

Question

At View → Sort by → Grouped By Sort you can activate the grouping of your mails by the chosen sort method. E.g. when you select the sort method "Date", you get groupings like "Today", "Yesterday", "Last Week", ….

These groups can be (un)folded by clicking at the little triangular icon (in some themes it seems to be a plus sign).

I observed several Thunderbird users that tried to unfold a group by double-clicking at the group heading (e.g. "Today") instead of single-clicking the little icon. I think this is natural behavior known from many other applications. However, Thunderbird won't unfold the group. Quite the contrary: Thunderbird opens all mails in this group. This creates two problems:

• all these mails are now marked as read
• it may take some time to close all the tabs again

After "Two Weeks" the next group heading is "Old Mail". This group might hold several thousand mails. You can imagine that it's no fun to see all these mails opened accidently.

Is there a (config) setting that disables this behaviour? If not, is there an add-on?

When the user double-clicks the group heading, the group should (un)fold (and never open all mails).

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I filed an issue: https://bugzilla.mozilla.org/show_bug.cgi?id=803997

Answer 1

Update (2016): I don’t know when it changed, but at least in Thunderbird 45, this is no longer an issue. Double-clicking folds/unfolds the group. No need for changing something in the config editor.

Old answer/solution:

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In Preferences → Advanced → Config Editor… you can set the option mail.operate_on_msgs_in_collapsed_threads to false (thanks, Joe Sabash).

This setting seems to "eliminate[s] the message summary in the preview pane", too.

Now nothing happens when you double-click at the group heading. Still missing is the functionality to (un)fold the group by double-clicking. The issue is there: https://bugzilla.mozilla.org/show_bug.cgi?id=531009