Exchange Online to block emails from vulnerable on-prem servers

Microsoft is introducing a new Exchange Online security feature that will automatically start throttling and eventually block all emails sent from “Persistently vulnerable Exchange servers” 90 days after the admins are pinged to secure them.

It will also be able to throttle and eventually block emails from Exchange servers that haven’t been remediated before reaching Exchange Online mailboxes.

This new enforcement system will only affect servers running Exchange Server 2007 using OnPremises connectors to send mail to allow fine tuning before expanding to all Exchange versions, regardless of how they connect to Exchange Online, after tuning the.

These enforcement actions are designed to slowly escalate until the vulnerable Exchange servers are remediated by removal from service or patched.

“The enforcement system is designed to alert admins about security risks in their environment, and to protect Exchange Online recipients from potentially malicious messages sent from persistently vulnerable Exchange servers.”

For some admins, ensuring that emails sent from vulnerable servers in their environment to Exchange Online mailboxes will not get automatically blocked will likely be another “Incentive” that will add to their ongoing effort to keep end-users protected against potential attacks.

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