http://www.safeit.com/products/fileenc/send secure attachments by e-mail without worries. The receiver of an e-mail with an encrypted file will only need the right password and a browser to decrypt the e-mail
Your data is converted into an encrypted html file which you send by email, the "killer application" is the recipient does not have to install any software : the decryption takes place in their browser via javascript. So it is independent of OS.