Microsoft says 92% of all Internet-connected on-premises Microsoft Exchange servers affected by ProxyLogon vulnerabilities are now patched and safe from attacks. A total of 400,000 Exchange servers were impacted when Microsoft issued the initial security patches, on March 2, with over 100,000 of them still unpatched one week later. Microsoft published additional security updates after March 11 covering over 95% of vulnerable versions exposed on the Internet and step-by-step guidance to help address these ongoing attacks.
Source: https://www.bleepingcomputer.com/news/security/microsoft-92-percent-of-exchange-servers-safe-from-proxylogon-attacks/