Common Ground
http://www.commonground.com
Although Common Ground does not develop or distribute e-mail software, you can obtain information about their document distribution products. These products, such as Common Ground Desktop Edition, enable you to convert Windows and Macintosh files to a common DigitalPaper format. You then can distribute that file over e-mail (or via a Web page, floppy disk, or network) to others and they can read and print your document, without worrying about which document or operating system the document was creating on.