I have a friend/client who writes articles in MS Office Word 2007 on Win Vista. He then pastes them into his gmail email in Firefox 3 and sends to publishers. When recipients receive the email, all special characters, including quotes, appear either as question marks or as square boxes. It even happens when he sends email to himself. (Yes, he could send attachments, but that would not resolve the problem).
I had him first save the docs in rtf format in Word, but the problem remains. I viewed source of the email I received - it specifies UTF-8 encoding.
This problem did not occur when he used Juno as an email client.