PDF attachment from Faxaway

I'm currently trying faxaway service, and I can receive the fax fine, but the problem is when I forward the file.

When I forward it from my Blackberry it's fine. But when I send it from my outlook or my webmail website; the file does not go through.

I contacted my ISP (Road Runner) and they don't have a clue. It seems to be that the PDF file is being filtered out by Road Runner.

Does anyone have any idea? Any help would be greatly appreciated.