Security researcher Kevin Beaumont discovered that a number of email servers for Trump’s hotels, golf courses, and other businesses are running badly configured, outdated versions of software that receive no security updates, and are lacking other security practices. Trump has so worryingly insecure internet setup that anyone with little knowledge of computers can expose almost everything about Trump and his campaign. The Trump Organization’s e-mail service only uses single-factor authentication, which means no Two-Factor authentication that makes a user link a device to receive an extra login code.
Source: https://thehackernews.com/2016/10/donald-trump-email-server.html