Exchange Online Cuts Legacy Links in 2023

• Exchange Online will block more connections from legacy technologies starting in 2023.
• The changes could help Exchange Online avoid attacks that have exploited security vulnerabilities in other systems.
• Organizations using Exchange Server versions before 2016 and Exchange Online PowerShell are most likely to see disruptions.

The Exchange Online cloud service will start blocking connections from older versions of the Exchange Server software and from some older protocols in Apr. 2023. As shown in the accompanying diagram, the changes will roll out through 2023. The changes will improve the security of the service, but they could also force some customers to accelerate their upgrade plans for on-premises systems.

Old Exchange Server Systems to Be Slowed, Blocked

Microsoft plans to slow and eventually block connections to Exchange Online from Exchange Server systems running unsupported or unpatched software, which it refers to as “persistently vulnerable” servers. Initially the policy will apply only to customers who have Exchange Server 2007 servers that connect to the customer’s Exchange Online tenant through an inbound on-premises connector. Customers might have this configuration to exchange mail with on-premises legacy devices such as networked multifunction printers that receive jobs or send results by e-mail, or to combine Exchange Online Protection cloud filtering with on-premises Exchange mailboxes.