Help with emailing files please.

Me and my friend both have Sonar Home Studio.  I would like to lay down a couple tracks and email the file to him and he can lay down some tracks.  Problem is, when i open his file or vice versa I get an error telling me about missing audio files.  What are we missing here?  Any help is greatly appreciated!  Thank you.

I do have the option to save as a cakealtk bundle - is that how i would save it, and then email that bundle?
 Thank you for your time - You are awesome!

Bundle file is a good option, even though they are more vulnerable to get corrupted than cwp-files.
I suggest you keep both cwp- and cwb-files  of the project updated. When you receive the bundle, save it as cwp when you have opened it.

If you prefer to use cwp, you must send also the audio files, not only the project cwp-file. I don't know if HS has "per project audio folders" as a saving option. If it has, you need to use it and send the whole folder.

The files may be so  big, hundreds of Mbs, that you need to use a transfer service site to manage the correspondance. I've never used those so I can't suggest one by name.