Microsoft has gained 20% in the last 12 months of the customers that make up the Fortune 500. ProofPoint’s growth over the same period was just 9%.
So even though ProofPoint has almost half the email security market, Microsoft is steadily growing at a faster clip than ProofPoint. All other email security vendors have declined over the past 12 months.

The two vendors make up for 72% of all the Fortune 500.

For my past blog posts on tracking the DNS records of the Fortune 500, including the ten reasons why I recommend Microsoft email security to my clients, click (here)