I'm going to make several guesses here; what you're doing, and what you're encountering.
The "C:\fakepath\" file path is usually a feature of a web mail system (and including the C:\fakepath\ string is part of the HTML5 web specs), and the Google Gmail web client was apparently reporting this with some versions of the web mail client; at least for a while.
Unfortunately, the things here are supposed to work this way, per the HTML5 specs. (Here's a discussion among some of the folks that were looking at HTML5. And here in the Apple forums, and here is a related discussion over at Microsoft.)
I don't know off-hand if this fakepath stuff has been changed again or not, as HTML5 specs have been a moving target.
If you're using a web mail client here (as I might guess), which one? It can be simplest to connect mail directly to the mail server, and use your Apple Mail.app client to read and write mail. With the identity of the web mail service (and if the mail service provider is not restricted to web-only access, and offers direct access), then somebody here may be able to help you connect to the mail server with the Mail.app client. This can entirely avoid the whole HTML5 fakemail mess.