KMail has an option (enabled by default IIRC) of “show emoticons as images” which actually translates text emoticons to the representing graphics when you are viewing a text email – this can be really annoying at times when you have stuff like “See here (note this):” in which case KMail decides it should render the last two characters as a frownie.
GMail does the same on chats, not sure about actual email.
Thunderbird has an extension that also shows text emoticons as graphics.

That being said, the obvious way to render the key strokes for ‘:’, ‘-‘ and ‘)’ in a text email isn’t as “J” 😉