I too could not get binary files to pass through my email clients.
The simplest answer for me was to use a PC to upload the files to a server. Then, any XO (or PC) could download them. Could not directly upload from XO because XO does not handle the user/password dialog of the server.
An account on the wiki with the upload (under Tools at the left side of any wiki page) might be an answer for you. I am not familar with the setting up of wiki accounts. Perhaps a start is :http://wiki.laptop.org/go/Contributing_content
If all else fails, I could set up an account on my server of the form http://xoserver.org/oceania
and supply you with a username / password as a temporary solution.
I hope someone else can supply us both with an email solution -- I could not find one.