This is a promising early version of a new Cocoa mail client combining the best of the Camino web browser and and the Mozilla Thunderbird email client, being written by one of Camino's developers. Correo promises to bring to email what Camino brought to web browsing: the power of Mozilla/Gecko technologies wrapped in the style/elegance and sensibilities of Cocoa.

Right now you can set up accounts and recieve and send email, but it seems like it's off to a good start.