Evolution grew out of desperation and Michael looked at the typical problems with Email today. Basically virtual folders are created on the fly as the need arises and messages can appear in any of them as long as they match the folder query. You can then integrate that with a task list and calendar so that such Emails can be entered in them right away. So, evolution is built of reusable bonobo components, it supports most of the existing standards for communication and its user interface is modeled after existing, known to be useable products. They then gave a demo of Evolution which was quite funny since the laptop that had all the data crashed, and the backup one they demoed on only had one message, which rendered the whole thing not very useful Evolution has an outlook-like interface and offers nice features like on the fly spell checking, HTML Email, and calendering just like outlook.
Evolution does look like a really cool mailer, and virtual folders seem very interesting.