Get Mail.app subject and message URL in a drag/drop operation

gistfile1.matlab

// In init or wherever:
    [self registerForDraggedTypes:
         [NSArray arrayWithObjects:@"public.url-name",nil]];

// In performDragOperation:
    NSString * subject = [[sender draggingPasteboard] stringForType:@"public.url-name"];
    NSURL * url = [NSURL URLFromPasteboard:[sender draggingPasteboard]];