Time to Ditch Your Old Exchange Servers
Microsoft is ramping up its focus on Exchange Server security, announcing that those outdated on-premises systems will soon be barred from sending emails to Exchange Online. Starting the second week in September, if you’re still operating Exchange Server 2016 or 2019 and relaying emails via an inbound connector of the OnPremises type, you must have it updated to the latest public update baseline released in October 2025, as stated by Microsoft. “This update level was rolled out nearly a year ago,” they indicated, “and all organizations should have transitioned to it.”
A New Standard Established for Exchange Updates
Microsoft has gradually been raising its “oldest acceptable version” standard for some time, but now it’s full speed ahead toward the last public update for Exchange 2016 and 2019. Any further increase would leave only those individuals in the Extended Security Update (ESU) program or those who have migrated to Exchange Server Subscription Edition capable of keeping pace.
A Dilemma for Hybrid Setups
Some users maintain on-premises Exchange servers to facilitate hybrid deployments, applications, or other systems reliant on them for email. Microsoft’s restrictions only pertain to servers sending emails to Exchange Online through an inbound OnPremises connector. Other delivery options remain unaffected, and the policy doesn’t apply to “all servers in your organization.” However, they did mention: “This may change in the future,” which sounds quite concerning, right?
The Perils of Security Patches
Admins find themselves in a challenging position needing to apply those security patches swiftly, but there’s always the potential that an update could bring about new issues – something Microsoft has been known for in the past. Some admins weren’t particularly pleased with the news, but throttling and blocking “severely outdated” Exchange Server iterations has been the norm for years.
Alert: It Was Inevitable
This announcement serves as a cautionary note regarding a change Microsoft believes would have occurred regardless. “With or without this announcement, the change would have been implemented (just as it has in the past, without any prior notice),” articulated Microsoft Principal Project Manager Nino Bilic. “The key takeaway is that admins really need to recognize that updating Exchange must be performed promptly.”
Conclusion: Update It, Buddy!
In the constantly spinning cycle of tech updates, Microsoft’s fundamentally urging everyone to fall in line and patch those old exchanges before they turn into relics. So, unless you prefer a heavy paperweight, make sure to hit those updates, everyone!
