Ruminations of a meandering mind

Correct me if iam wrong, but the word "Prepone" does not exist. Its merely a concocted opposite of postpone. This was brought to light by a friend of mine recently but I continue to use this word frequently. I have seen it being used( quite judiciously of course) in formal meetings,emails etc without( or with) people having an inkling about the authenticity of the word. But then, probably this is one among many such words. Also, does it really matter whether the words that we use everyday need to be listed in the dictionary. I dont think so. As long as the people you are communicating with know what you mean when you speak or from whats written in your mail, I guess there's no issue at all.