Update October 20, 2026: Added a FAQ to this post.
Since October 13, 2026 (Microsoft “Patch Tuesday” release cycle), we have seen some reports of customer issues where Exchange Servers become unsta...
Updated Oct 20, 2026
Version 3.0
Blog Post
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Exchange servers may become unstable after installation of October 2026 Windows updates
Thanks for sharing this, very helpful.
You mentioned that the number of used contexts dropped from 512 to 0 after stopping the Microsoft Exchange Health Manager service. How did you check that number? Is there a performance counter, a command, or a tool that shows the current number of saved contexts in the RPC Endpoint Mapper?
Background: We were hit by this issue on several Exchange SE servers after the October updates. We have now set EpmapSavedContextCap to 65536 on all servers, and they have been stable since. We would like to monitor the current value regularly, so we can see how fast it grows and whether we are getting close to the limit before the next planned reboot.
AFAIK perfmon or other normal tools can't get the information. I found a reddit post with a powershell script that works for us. You just need to know the dll file version and correct offsets for that to get the details out from the system. They can all be found on that post.