When starting a drag in the message list and then dropping it on the message list again, KMail should do nothing. Instead, it pops up a context menu saying "Copy Here/Move Here", which doesn't make sense. (Ideally, it should say "Move message to this thread" and re-thread the message, but that is out of scope of this report)
SVN commit 1152561 by mlaurent: Fix bug #223826 - Dropping message to message list shouldn't give popup menu BUG: 223826 M +3 -1 widget.cpp WebSVN link: http://websvn.kde.org/?view=rev&revision=1152561