Microsoft to bounce mail from outdated Exchange servers
- ID
- 21504
- Status
- summarized
- Published
- 04 Sep 2026, 9:43 PM
- Fetched
- 04 Sep 2026, 10:46 PM
- Provider
- The Register
- Category
- technology
- Original URL
- https://www.theregister.com/on-prem/2026/09/04/microsoft-to-bounce-mail-from-outdated-exchange-servers/5294506
- Source URL
- https://www.theregister.com/headlines.atom
Summary
- Score
- 4.0
- Created
- 04 Sep 2026, 10:47 PM
- Tags
- Audience
- saas_foundersdevelopers
What happened
Microsoft will begin blocking email from Exchange Server 2016 and 2019 installations that are not patched to the October 2025 baseline starting the second week of September 2026. The policy applies to servers sending email to Exchange Online via an inbound OnPremises connector, though other delivery methods are unaffected. Microsoft Principal Project Manager Nino Bilic noted that this baseline update would have occurred regardless of the announcement.
Why it matters
SaaS founders or IT admins using on-prem Exchange 2016/2019 for hybrid email must ensure their servers are updated to the October 2025 baseline or risk having their mail to Exchange Online blocked starting September 2026.
Discussion angle
How relying on legacy on-prem infrastructure for critical communication like email creates forced upgrade paths and potential single points of failure for SaaS operations.