tones

If they received it as AMR then they should be able to open it w/ voice recorder automatically and save it. If it streamed, then it sounds like it has a streaming header (opening real or whatever). It's probably just nokia's stupid DRM system. Get Fexplorer, change the filename, send it have your friend change it back.

If it is a ringtone you purchased that you are trying to send it may not be possible as a lot of providers but restrictions in them to stop you giving it away for free.