Several years ago, we announced Throttling and Blocking Email from Persistently Vulnerable Exchange Servers to Exchange Online. Since then, we have been periodically updating the “oldest acceptable v...
Updated Sep 02, 2026
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Blog Post
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Exchange 2016/2019: Throttling and Blocking up to the Final Public Update Baseline
Does the "starting in the second week of September 2026" mean 9/6, 9/7 or 9/13, 9/14? In any case giving this short of notice of a potentially breaking change is crazy work. Fully aware of the enforcement pausing as linked above. But this forces non-compliant orgs to start burning those 90 days. Just my 2 cents.
Addendum:
Adding that stage 1 (no throttling/blocking) of enforcement is 30 days. Would be good to know if any notice to admins (GA?) is sent when this is enabled in their tenant. Message Center, email, carrier pigeon?
- Nino_Bilic
Microsoft
Just to be clear: we never pre-announced the "moving the version higher" like we did today. So with or without this announcement, the change would have been made (just as it was made in the past, without any announcement). My expectation of the time of change is mid week next week. But it is a service change and nailing this down to exact day / time in a global service is hard.
But yes - this forces organizations who are on versions older than October 2005 to start their 90 day countdown. Exactly the point of this change. Honestly, a really good argument could be made that we should move past October 2025 right now (seeing how much security payload we released this calendar year).
The bottom line is that admins really need to understand that updating Exchange should be done on time.
