Microsoft is introducing a new feature that aims to stop emails from being sent from vulnerable Exchange servers. The entities identified as persistently vulnerable are those that have reached the end of life or remain unpatched for known vulnerabilities, such as Exchange 2016 and 2019. This is part of Microsoft’s ongoing effort to help protect its users from any potential harm caused by malicious emails. 

In order to start blocking potentially harmful emails, the new feature will first throttle all messages sent from these at-risk entities before eventually cutting off access completely. This process will be done gradually in order not to disrupt customers' networks or affect their user experience too much. 

At the same time, Microsoft has also stated that it will be providing guidance on how companies can patch their systems and stay up-to-date with security updates in order to avoid having their emails blocked altogether. Additionally, they have also promised that this new feature will be supported by other tools such as Office 365 Advanced Threat Protection (ATP).  

Microsoft has also emphasized that this measure is being taken in an effort to better protect its users rather than punish them for not staying up-to-date on patches and updates. They hope this move will encourage those who may not have been aware of the threat posed by vulnerable Exchange servers so far to take the necessary steps towards protecting themselves against malicious actors looking to exploit them through email attacks. 

All in all, it's clear that Microsoft is taking proactive measures when it comes to protecting its users against potentially harmful emails coming from vulnerable Exchange servers. It remains unclear whether this move alone can guarantee complete safety, but it's certainly a positive step towards improvement when it comes to online security and protection measures used within organizations today.