Simple answer from me - no you can't do what you're trying to do. you can only save music into your own ( or a shared) library for listening to later on or off line, but you can't "save and export / send" to other people.

From Google...
"Spotify is not designed to download Music in MP3 or WMP Format. What you can do is activate the "Offline Mode". This will download the songs in a proprietary format which you can play back with your Smartphone, PC/Mac or iPod Touch using the Spotify Application. You can however not extract songs into other formats."