The Temporary Path is a better place to store things like that. By definition, users have write access. And it doesn't affect a user's desktop. To export to that place, use a script such as:
Set Variable [ $temppath; "file:" & Get ( TemporaryPath ) & "/photo.jpg" ]
Export Field Contents [ Table::containerfield; "$temppath" ]
Then you can pick up the image using a similar structure to create a variable and specify that in the Send Mail attach file.
See how that works?
I hadn't thought of that. Sounds like a better solution than mine. I'll let you know how it goes when I get it set up.
Your idea works great. Thanks for the easy solution.