I've tried 'right clicking' drag-n-release several times... in Chrome... all is does is move it.
...and then other times.. it works... different machine.. same type of browser.
A little frustrating to say the least.
Also verified that in the documentation,
http://help.smartertools.com/SmarterMail/v12/Default.aspx?p=_USR&v=12.2.5269&lang=en-US&page=main/frmmessages
doesn't reference any copy actions as well