Don't they use something similar to verify Wikileaks documents?
I was wrong:
https://www.wikileaks.org/wiki/WikiLeaks:About#How_does_WikiLeaks_test_document_authenticity.3F
"WikiLeaks staff examine all documents and label any suspicions of inauthenticity based on a forensic analysis of the document, means, motive and opportunity, cost of forgery, what the authoring organization claims and so on. We have become world leaders in this and have an enviable record: as far as can be determined, we have yet to make a mistake. This does not mean we will never make a mistake, but so far, our method is working and we have a reputation to protect."
I think I was confused, because they used google user information on the emails to verify them or something. Apologies.
https://www.allacronyms.com/pain/Privacy%2C_Authentication%2C_Integrity_and_Non-repudiation
https://www.quora.com/What-is-authentication-integrity-and-non-repudiation-in-the-field-of-computer-security
https://technet.microsoft.com/en-us/library/cc700808.aspx
Literally took me a few seconds on duckduckgo.
If you can't be bothered to do your own research and verify, then you shouldn't be here. If someone is making a claim that is unsubstantiated, you ignore them, not spend time asking for information when you could look it up yourself.