Version: (using KDE KDE 3.5.8) Kmail is more complex app that an editor with one document, so please do not show menu entry undo which tells nothing, but undo (delete 3 inbox messages) This way user can be sure she/he won't do any harm by undoing not known/remembered action.
Thank you for your feature request. Kmail1 is currently unmaintained so we are closing all wishes. Please feel free to reopen a feature request for Kmail2 if it has not already been implemented. Thank you for your understanding.
Instead of creating a new feature request, please confirm here if the wishlist is still valid for kmail2.