Add the upload module, if not already there.
In editor click on the field and on the right side click Field Properties.
Select 'Send File as Email Attachment ' or ' Enable Advanced Uploader'
Advanced uploader works better, I think as file size is not an issue. You'll get a link to the file, instead of the file itself.
'Send File as Email Attachment' should work but you need to rely on both mail hosts to deal with the files properly and if they are too big or to many, they might not get delivered.
Nevertheless, this is where the options are.