DKIM is a system designed to stop spam. It works by verifying the sender of the email. Moreover, as a side effect, it verifies that the email has not been altered.

Hillary’s team uses “hillaryclinton.com”, which as DKIM enabled. Thus, we can verify whether some of these emails are true.

Source: Errata Security: Yes, we can validate the Wikileaks emails

I was just listening to ABC News about this story. It repeated Democrat talking points that the WikiLeaks emails weren’t validated. That’s a lie. This email in particular has been validated. I just did it, and shown you how you can validate it, too.