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
3 MIN READ
Exchange servers may become unstable after installation of October 2026 Windows updates
I am planning to install the October patches and apply this registry setting on my Exchange server over the next few days.
However, my environment has around 700 users who rely on Exchange services continuously.
Could you confirm whether “65536” is sufficient? If I double the value, what impact will it have? What is the maximum value?
I sincerely hope to hear from Microsoft as soon as possible. Thanks.
I tried doubling the value before contacting support. Did not work for me.
- Nino_Bilic
Microsoft
Yes, that value will be appopriate.
Hi Nino, Thanks for your reply.
May I ask whether setting the value to double the current value would have any impact?
- Nino_Bilic
I neve heard of anyone needing a larger value.
We have some 25,000 mailboxes in our environment and we have had no issues with the registry fix, with the value 65536.
