Update October 16, 2026: For more information related to installation of October 2026 updates for Windows Server and the possible impact on Exchange Server, please see Exchange servers may become uns...
Updated Oct 16, 2026
Version 7.0
Blog Post
There are reports that "reg add "HKLM\SOFTWARE\Microsoft\Rpc" /v EpmapSavedContextCap /t REG_DWORD /d 65536 /f" is at least a temporary workaroud to extend server runtime beyond the current 22 hours or so.
Where is Microsoft? This has been an issue for 3 days. There are thousands of hybrid installations still out there. Any official word from Microsoft going into the weekend would be appreciated!
Nino_Bilic
Microsoft
MicrosoftWe are aware of the registry key. It is a temporary relief, and it is not "unsafe" for your server. But it might not be the final way to solve this either.
We are still waiting for the official guidance from Windows team and will provide it when we have it. I know it might seem pedantic, but while we want to provide guidance to Exchange customers, we need to get the right guidance from Windows team in this case, as it is a Windows update that changed the setting here.
It is not a satisfying answer for anybody; as soon as I have official guidance that we can share and has been bought off, we will share it.
Also please note that not nearly every server will run into this problem; this has to do with server peak load and exhaustion of resources over time (which is why a reboot solves the problem for a while). Some Exchange servers will never see the problem at all.
Hi Nino,
thx for providing updates where you can. The reason I patched OS win update for October was also because it contains a time zone update/change specific to my region. Now I had to roll it back and hope before November there is going to be a fix. Luckily it was non prod servers I tested and also that most of our prod users are in EXO (they are now unlucky as well due to a botched tz setting). Still have some on prem. Also not related the new time zone available in EXO user mbx settings is buggy (our region decided to go permanent in March this year...west coast somewhere). Free busy will stop working for the users that have switched to the new time zone (work hours and location bug) . There are literally tens of thousands of MS customers affected by this. MS Ticket ongoing with support clueless. Imagine Teams, MS Bookings and the rest of products. Just some feedback from my end.
You guys can keep waiting, but it's ignoring the fact that we have production systems that we pay expensive SE licensing for. We shouldn't be going days in the dark with no suggestions. The blog should at minimum have the registry potential fix that delays the problem and at minimum be telling us that a reboot works for 24 or 22 hours or however long it works for (generally). Flying completely blind relying on 2nd hand 3rd hand information off of reddit and other forums is the kind of support level I'd expect from unlicensed, open-source software not enterprise software running production. Businesses need to keep receiving email so we can't have it suddenly stop working with no resolution. You guys need to do better. Similarly, I have the same kind of problem with Azure DevOps Server not fully supporting .NET 10 in build pipelines -- nearly a YEAR later. Instead, we're relying on some kind soul who is maintaining a separate plugin lineage for the build agents. It just feels like Microsoft is slowly abandoning on-prem solutions.
At this point real guidance is needed with clear instructions on how or what we need to do to remedy this.
I would describe the response from Microsoft as pathetic rather than pedantic.
Any idea what would make Exchange servers different with regard to resource exhaustion? Number of mailboxes or centralized message tracking or ?
