I just read an article on Law.com entitled Can RPost Registered E-Mail Save You From Disaster in the Courtroom? The article discusses RPost, a service that creates a copy of an email and a receipt that is admissible in court —
In actuality, RPost protects the sender with proof of their entire e-mail transaction by providing a registered receipt (which is legally valid evidence) that your registered e-mail was sent; that it was received and when that took place. It also verifies the content of the e-mail message sent, including all the attachments!
If you think that RPost could not be the standard that your next trial might just need, consider this: the Federal Government has tested, approved and accredited RPost, and they use it in the arm of Congress known as the GAO (Government Accountability Office).