By default, Thunderbird 3 uses strict threading which means that threading by subject is disabled. There are two settings that control this behaviour though: mail.strict_threading and mail.thread_without_re. The first setting enables/disables threading by subject while the second allows subject-threading even if “Re:” isn’t present. There is also a setting new to the 3.x branch called mail.correct_threading which threads correctly regardless of the order messages are added to a folder.
All of this means we need to toggle the three thread-related settings from their default value in order to get the behaviour I expect. To do so we go to Edit -> Preferences -> Advanced -> Config Editor. After promising to be careful we filter for “thread” and observe the following settings and their values:
- mail.correct_threading with default value true
- mail.strict_threading with default value true
- mail.thread_without_re with default value false
Now we double-click each of these to change their value and close the dialog. Then for each folder we need to go to Edit -> Folder Properties -> Rebuild Index. Now Thunderbird 3 should display messages in each folder threaded in exactly the same way as had the previous version!
bonus tip for ThunderBird 2
In TB2 if you are viewing messages in threaded view, clicking on a column name (other than the thread column) will turn off threaded view. If we want to keep threaded view on we must go to the Config Editor as above, search for the preference mailnews.thread_pane_column_unthreads and double click to change its value to false. In TB3 this is by default set to false so not change is needed.
Tags: Thunderbird
