Drag and Drop directly from Outlook to a webform
I found this sample WebApp where you can drag and drop Outlook Contacts to an HTML5 WebForm.
If you drag an Outlook Message directly from Outlook to the WebForm you can drop it, but nothing happens. Maybe with a little tweaking you can get it to work with Messages too.
AT this moment drag-and-drop API in Internet Explorer Browser isn't supported, Microsoft will implement it in IE 10, but i don't know if Drag-And-Drop API will bring you with the functionality that you are looking for.
For the rest of browsers the API implementation is incomplete
i recomend you to considere alternatives to this approach