Version: (using KDE KDE 3.2.0) Installed from: Gentoo Packages It seems that the option to thread an individual folder's messages by subject should be in the properties page for the folder, (maybe with the "folder contains mailing list" option - since most people probably thread their messages for their mailing list folders). The option is in the menu under "Folder", but it just doesn't seem that's the first place that people would look. (I know that I looked forever for it, until I finally posted the question to kdepim-users)
I second this bug report. The handling of the "treading" setting is KMail is just not intuitive. In response to this report, perhaps the setting should instead be under "view" or in the "properties..." dialog of a particular folder. Additionally, it is very difficult to find this setting in the KMail preferences window. It is currently located under Configure KMail... -> Appearance -> Headers -> Thread List of Message Headers This makes absolutely no sense to anyone but the person who programmed it. There are two natural relocations for this feature. #1. Sort Mutt handles threading as a sort option. You "sort by threads" which makes sense to a lot of people. KMail lacks a dialog for sorting and it is kind of a hidden feature in the message list (click on column title) so I am not sure how well this would fit in. #2. Folder View If there is going to be a menu item for "Folder" at least put the thread messages (and leave off the part about the headers) in the Folder preferences dialog so that it is consistent with the menu. Configure KMail... -> Folders #3. open to other ideas...
What about the context (right-click) menu of each folder? That makes the most sense to me....
*** This bug has been marked as a duplicate of 37771 ***