Since KDE 3.5.3 KMail has "Jump to folder" which is bound to 'j' by default. So if you want to quickly go to a folder you press j, then you (partially) enter the name of the folder you want to go to and then you press Return. IMO this is a better solution than a quick search for the folder list because it doesn't require switching between mouse and keyboard. I hope you agree.

I don't agree. You could implement a search box which also does not require to change between keyboard and mouse: a 'j' would activate the search box (or you could click into it with the mouse), you begin typing and the folderlist shortens. Then you hit enter when you have found your folder - no need to use the mouse but you wouldn't be bound to use the keyboard to activate the filter which means more freedom for the user.

That j-way is more complicated to use because you don't see it and its usage and look are confusing. That path it shows is irritating and unnecessary. A simple quick search filter box would be much more convenient and clear. Why changing the look of the folder list while searching? Also a search box looks more common and can be easily found by anyone, even people new to KDE/kmail. Please make the search option visible.

Also it would be possible to paste text into a search box with the middle mouse button so you are not forced to use the keyboard. And with a search box I don't need to remember to type a "j" in front of every folder when searching. I just could click into the search box (right hand on trackball) and begin typing what I have in mind with the left hand. No need to "think around the corner".

I really would prefer a search box for the folder list but please at least give the user the option to get rid of that irritation path in the j-search.

Oh by the way: that's an inconsistent behaviour, having search boxes in several parts of the application and having to press a key for searching in one other part. Inconsistent behaviour confuses the users.

Thanks for implementing it in KDE 3.5.9.