It's not about email; it's about people who are careless in their choice of apps/services
"Precisely because it’s inescapable, insecure and irresistibly convenient, email provides an almost uncomfortably intimate view into the historical record. It preserves time, location and state of mind, the what-when-where-and-who of every story we might want to dig up. The last two decades, email’s high-water era, have thus been a bounty for anyone wishing to understand exactly what was happening in the inner circles of powerful organizations — for journalists, historians and prosecutors of white-collar crime, among others.
If common sense prevails, Mr. Trump’s email thread may serve as the final nail in the coffin of email as the universal office communicator. People in business and politics are already moving on to other methods, from cloud-based business tools like Slack to apps like Signal, which promise the discretion of a spymaster. These tools allow for auto-deletion and encryption; they’re not perfectly secret (nothing is), but they’re a fortress compared with email."What We Lose When the World Moves On From Email - The New York Times