Umm, that's not a standard Magento file.
Where is it supposed to be found?
Was it a backup of your Magento system that one of your developers made?
And if it was originally in your web server's doc root folder system, why was it left there? (security breach issue)
And if it's really what I think it was, GMail will only accept 10MB worth of file attachments so you'll need another method to move it.
