Phishing attacks, which trick users into revealing sensitive information or installing malware, have grown more sophisticated and localized. Putting it simple: the frauds you'll get in Portugal are completely different from US, Singapore or any other place. 

As the largest players in the email space acknowledge the need for DMARC, the entire ecosystem will become restricted to the ones following the rules. 

A number closer to 4 out of 5 companies use Exchange (cloud or onprem). Think about the massive infrastructure. Imagine how important and prevalent it is for businesses....and realize why it is constantly targeted by attackers. Businesses should carefully evaluate the risks and limitations of relying on Exchange as their security email solution as well as their storage and communication email solution.