Cool demo, but the evil me considers connecting it up to the production mailing cluster we have and seeing how it would handle a few hundred messages a second....
I would be interested to know what kind of performance you do get out of this (i.e. messages a second) as I've been writing code to do some SMTP handling in python and been looking for a way to speed it up.
I like how it get's around the problem of storing images people send before serving the <img> tag to the browser (for people who don't want to look: it doesn't store the images at all - it serves them in the same websocket stream using data: urls)
The application cannot handle the character encoding that you sent it. Go does not have a standard library for converting arbitrary character encodings to UTF-8. Perhaps this will demo will illustrate the need for such a library.
Very good to target HN demographics :o)