WP 8.1 supports file picker, Onedrive already supports it but WP's mail client still doesn't support it. MS has made Xbox Music & Video as separate apps and not included em in system apps but no progress in mail client part. WP's mail client is pretty basic, yes I know we can even send multiple files with the help of "Files" but mail client itself can't attach multiple files. Should MS also make Mail Client as a store app instead of a system app so it can frequently update it with new features and bug fixes ? If WP wants to be leader in enterprise, it should embrace good full featured mail client. Even Office Mobile also needs to be store app instead of system app.