DMARC is an open standard that helps secure corporate email accounts against impersonation. Only a quarter of corporate domains had DMARC enforcement mechanisms in place, report says. DMARC can be tricky to set up, especially when companies use outside providers for marketing, human resources, payroll and other services where the vendor sends emails on the company’s behalf. Of the Nasdaq 100, 43 percent attempt authentication, as do 25 percent of FTSE 100, 24 percent of the S&P 500, and 16 percent of Fortune 1000.”]