Steps to reproduce & Actual results
drag&drop an e-mail into a folder => e-mail is moved into the folder
drag&drop a contact into a contact group => the contact is copied into the group
Expected results
The drag&drop fuction should have a similar result all over the program
solution
Folders and groups represent two different conceptual models. Hence the two different outcomes of the drag&drop function may make sense. Nonetheless a short feedback about what has happened (e-mail has been moved to xy, Contact has been added to the group xy) woud be helpful.