Donna Brazile likes to claim that the emails like this one were “doctored”. Nope. Somebody configured hillaryclinton.com to use DKIM, so anybody on the internet can verify for themselves that Ms. Brazile was indeed sent the debate question she lies was never sent to her.
More details are available on several web sites.
UPDATE: they finally got around to changing their key. Today (26 October 2016, in case I need to update again). Six days after people started proving that they were lying about Wikileaks supposedly falsifying evidence. If the key had actually been compromised, that would have happened on the day of the interview, at the latest.
I am truly shocked. I was just assuming that, after all these years of practice, Team Hillary would be at least marginally competent at bullshit. Obviously, I was wrong.