Sure, you could say the same of any document, electronic or not. Most crime is not that complicated.

  It turns out that the metadata footprint left on a computer creating a document- if you can seize it- is rich in detail enabling creation date and the like to be identified. Mail servers may hold logs. Often a fake email or document is part of an offense and proving where a faked email was sent from becomes quite relevant, and yes, ends up as evidence in court.

You may hear a prosecutor say "and on the 30th of june 2011 did you send the following email..blah..blah"

There is a reason for that- they are establishing the possibility that it is actually evidence. Its not clear cut, otherwise we wouldn't have courts. You proffer evidence and convince people of it's weight. And that will continue to be the case.

> I always wondered why emails were evidence. They're just text, anyone could fake an email.

The right question isn't usually if they could, but how likely it is they would. Also, I do hope cases aren't usually hinged on a single e-mail, but include other evidence that together paints a coherent story.

IANAL but I expect emails are only evidence to the extent that the other party acknowledges (or at least, doesn't object to) their veracity. If they do object, then you can have fun tracking down logs and stuff. Of course, that's also just text, so if that's called into question, you start questioning the people involved in maintaining the logs, etc, and trying to figure out which story is more plausible. So in short, what courts do on a daily basis anyway. All evidence is circumstantial to some extent.