mistake in article
it's DKIM not DKIF
Following a recent spate of incidents in which high-profile accounts have been compromised by hackers, Twitter has implemented a security protocol designed to make it harder for fraudsters to send out emails that appear to come from Twitter.com addresses. "We send out lots of emails every day to our users letting them know …
this is where the DKIM comes in - DKIM signatures remain valid so long as the message is forwarded verbatim
DMARC allows one of SPF and DKIM to fail without the message being rejected - it can be seen as combining the strengths of the two systems and avoiding the weaknesses