Autosave feature exists or not?

I can’t find any current information on whether or not there is an autosave featurue. I keep getting sites that announce the introduction of such a feature, but then don’t explain how to enable it. There are plugins that do this, but only if you use WP 1.5.

So, does anyone know if this really is built into the core? If so, how does one enable it? If not is there a plugin that currently works?

I set up a blog so that my brother and sister-in-law don’t keep sending 10 page emails, but she won’t use it because there’s no autosave feature. (also, apparently her parents only want to read emails, and no amount of me explaining that she can include the entire post text in the email notifier will convince her… but that’s beside the point)