dragging mail from message list to mailfolder with subfolders

In KDE 3.5.10 I could drag an email from the message list (inbox or 
whatever) to a folder in the folder list, and if there were subfolders 
on a folder I "hovered" over for a while the folder would neatly expand 
and I could drop the mail in any chosen subfolder.

In KDE 4.3.3 this does not seem to work, the folders do not expand but I 
have to make sure the folder list is expanded before I drag and drop an 
email.

Is there a setting somewhere that I am yet to find or has something 
"gone missing"?

Kind regards
Sinclair