Version:           1.11.4 (using KDE 4.2.4)
OS:                Linux
Installed from:    Slackware Packages

Dragging a message from the message list over to a directory in the directory list which contains a sub-directory do not make the parent directory open. One must click on the plus(+) sign near the directory before to show its sub-directory, and then drag&drop the message into the sub-directory.

Steps to reproduce:
1. Make the parent directory.
2. Make a sub-directory under the previously created parent directory.
3. Make sure the parent directory shows the plus(+) sign, so it's not expanded.
4. Drag a message from somewhere and try to drop it in the sub-directory. => the parent directory won't open up, ie. in the directory list tree it won't expand, instead it stays collapsed. <= the bug.