Windows 11 25H2 causes Outlook desktop indexing to fail and hang


B

BirendraN

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OS
windows 11
I installed 25H2 on 17 OCT 2025
My Build is Version 25H2 Build 26200.6901.
PC: Microsoft Surface 7 Snapdragon(R) X 12-core X1E80100 @ 3.40 GHz (3.42 GHz)

Ever since then the Windows Search service correctly indexes files/folders/documents etc. on my hard disk.
As soon as I start Outlook, that causes the indexing to stop both within and without Outlook.
Outlook build is: Version 2509 Build 19231.20216 Click-to Run
All Office updates have been applied and all Windows updates
The Event Log is full of Event ID 1000 - see attachment.
This is a real problem; the issue persists even after Rebuilding the Index.

1. Is this really a known issue which Microsoft is investigating please?
2. Any advice how to rectify this?

Thanks
 

Attachments

My Computer

System One

  • OS
    windows 11
    Computer type
    Laptop
Something to try: Apparently you can tell Office not to use App-V subsystems which from what I can tell is the issue, using this reg tweak (create it)


Fix Event ID 1000, AppvIsvSubsystems64.dll
Registry Fix:

Code: 
Windows Registry Editor Version 5.00

; Disables App-V integration for Office Click-to-Run
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\ClickToRun\Configuration]
"AllowAppVSubsystems"=dword:00000000

  • Open Notepad.
  • Paste the code above exactly as shown.
  • Go to File > Save As.
  • In the Save dialog:
    • Set File name to: DisableAppV.reg
    • Set Save as type to: All Files
    • Click Save
  • Right-click the saved file and choose Merge.
  • Confirm the UAC prompt and restart your PC.
This registry key tells Office to bypass its virtualization layer (AppvIsvSubsystems64.dll), which is known to crash SearchProtocolHost.exe on recent builds.
 

My Computers

System One System Two

  • OS
    Windows 11 Pro 25H2 Build 26200.8655
    Computer type
    PC/Desktop
    Manufacturer/Model
    Sin-built 2013
    CPU
    Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
    Motherboard
    ASUS ROG Maximus VI Formula
    Memory
    32.0 GB of I forget and the box is in storage.
    Graphics Card(s)
    Gigabyte nVidia GeForce GTX 1660 Super OC 6GB
    Sound Card
    Onboard thingy
    Monitor(s) Displays
    5 x LG 25MS500-B - 1 x 24MK430H-B - 1 x Wacom Pro 22" Touch Screen Tablet
    Screen Resolution
    All over the place
    Hard Drives
    Too many to list.
    OS on Samsung 1TB 870 QVO SATA
    PSU
    Silverstone 1500
    Case
    NZXT Phantom 820 Full-Tower Case
    Cooling
    Noctua NH-D15 Elite Class Dual Tower CPU Cooler / 6 x EziDIY 120mm / 2 x Corsair 140mm somethings / 1 x 140mm Thermaltake something / 2 x 200mm Corsair.
    Keyboard
    Corsair K95 / Logitech diNovo Edge Wireless
    Mouse
    Logitech: G402 / G502 / Mx Masters / Mx Air Cordless
    Internet Speed
    2000/500Mbps
    Browser
    All sorts
    Antivirus
    Kaspersky Premium
    Other Info
    ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
    TP-Link BE9300 WiFi 7 Bluetooth 5.4 (Archer TBE550E)
    TP-Link TX201 V1 2.5GB Lan

    Grandstream HT812 - VoIP
    ASUS DSL-AX82U - Mesh
    ASUS RT-AC68U - Mesh
    ASUS RT-BE88U Router

    Brother MFC-L2880DW Printer

    I’m on a horse.
  • Operating System
    Windows 11 Pro 25H2 Build 26200.8655
    Computer type
    Laptop
    Manufacturer/Model
    LENOVO Yoga 7 14IRL8 - 7i EVO OLED 14" Touchscreen i5 12 Core 16GB/512GB
    CPU
    Intel Core 12th Gen i5-1240P Processor (1.7 - 4.4GHz)
    Memory
    16GB LPDDR5 RAM
    Graphics card(s)
    Intel Iris Xe Graphics Processor
    Sound Card
    Optimized with Dolby Atmos®
    Screen Resolution
    QHD 2880 x 1800 OLED
    Hard Drives
    M.2 512GB
    Antivirus
    Defender / Malwarebytes
    Other Info
    …still on a horse.
Thanks for the help. I really want to know if Microsoft are aware of this issue and are going to rectify it themselves. I could not see anything listed on the 25 H2 known issues page.
 

My Computer

System One

  • OS
    windows 11
    Computer type
    Laptop
BirendraN said:
Thanks for the help. I really want to know if Microsoft are aware of this issue and are going to rectify it themselves. I could not see anything listed on the 25 H2 known issues page.
Click to expand...

No idea, sorry. I gave up wondering what Microsoft knows after DOS or Windows 3.1, I can’t remember which.

Feedback hub might have other reports?
 

My Computers

System One System Two

  • OS
    Windows 11 Pro 25H2 Build 26200.8655
    Computer type
    PC/Desktop
    Manufacturer/Model
    Sin-built 2013
    CPU
    Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
    Motherboard
    ASUS ROG Maximus VI Formula
    Memory
    32.0 GB of I forget and the box is in storage.
    Graphics Card(s)
    Gigabyte nVidia GeForce GTX 1660 Super OC 6GB
    Sound Card
    Onboard thingy
    Monitor(s) Displays
    5 x LG 25MS500-B - 1 x 24MK430H-B - 1 x Wacom Pro 22" Touch Screen Tablet
    Screen Resolution
    All over the place
    Hard Drives
    Too many to list.
    OS on Samsung 1TB 870 QVO SATA
    PSU
    Silverstone 1500
    Case
    NZXT Phantom 820 Full-Tower Case
    Cooling
    Noctua NH-D15 Elite Class Dual Tower CPU Cooler / 6 x EziDIY 120mm / 2 x Corsair 140mm somethings / 1 x 140mm Thermaltake something / 2 x 200mm Corsair.
    Keyboard
    Corsair K95 / Logitech diNovo Edge Wireless
    Mouse
    Logitech: G402 / G502 / Mx Masters / Mx Air Cordless
    Internet Speed
    2000/500Mbps
    Browser
    All sorts
    Antivirus
    Kaspersky Premium
    Other Info
    ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
    TP-Link BE9300 WiFi 7 Bluetooth 5.4 (Archer TBE550E)
    TP-Link TX201 V1 2.5GB Lan

    Grandstream HT812 - VoIP
    ASUS DSL-AX82U - Mesh
    ASUS RT-AC68U - Mesh
    ASUS RT-BE88U Router

    Brother MFC-L2880DW Printer

    I’m on a horse.
  • Operating System
    Windows 11 Pro 25H2 Build 26200.8655
    Computer type
    Laptop
    Manufacturer/Model
    LENOVO Yoga 7 14IRL8 - 7i EVO OLED 14" Touchscreen i5 12 Core 16GB/512GB
    CPU
    Intel Core 12th Gen i5-1240P Processor (1.7 - 4.4GHz)
    Memory
    16GB LPDDR5 RAM
    Graphics card(s)
    Intel Iris Xe Graphics Processor
    Sound Card
    Optimized with Dolby Atmos®
    Screen Resolution
    QHD 2880 x 1800 OLED
    Hard Drives
    M.2 512GB
    Antivirus
    Defender / Malwarebytes
    Other Info
    …still on a horse.
I can't understand You have been using Windows Search, as it's has always been slow and more or less useless.
The search and index tool Everything will open a new world for You. You have to use a little time configuring it
to your needs, but the you will have a search "Switzer-Knife" :

I use it home and at work, as it also able to index network drives, Google drive etc.

Everything
 

My Computer

System One

  • OS
    Windows 11 Pro
    Computer type
    PC/Desktop
    Manufacturer/Model
    Homemade by me
    CPU
    Intel i5 12600K
    Motherboard
    MSI PRO Z690-A DDR4
    Memory
    G.Skill Ripjaws V DDR4 3600 MHz / PC4-28800 CL16 2x8 GB
    Graphics Card(s)
    Intel® UHD Graphics 770 (iGPU)
    Sound Card
    8-Channel (7.1) HD Audio
    Monitor(s) Displays
    Legion/Lenovo Y25-25
    Screen Resolution
    Full HD 1920 x 1080
    Hard Drives
    WD Black NVMe M.2 500 GB (system drive)
    Case
    Lian-Li
    Keyboard
    Old solid and heavy IBM🙂
    Mouse
    Logitech
    Internet Speed
    1000 mbit
    Antivirus
    Avast free
Jorgen E said:
I can't understand You have been using Windows Search, as it's has always been slow and more or less useless.
The search and index tool Everything will open a new world for You. You have to use a little time configuring it
to your needs, but the you will have a search "Switzer-Knife" :

I use it home and at work, as it also able to index network drives, Google drive etc.

Everything
Click to expand...

The issue is Office using App-V subsystems and there’s a conflict. Not how well Everything search works.
 

My Computers

System One System Two

  • OS
    Windows 11 Pro 25H2 Build 26200.8655
    Computer type
    PC/Desktop
    Manufacturer/Model
    Sin-built 2013
    CPU
    Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
    Motherboard
    ASUS ROG Maximus VI Formula
    Memory
    32.0 GB of I forget and the box is in storage.
    Graphics Card(s)
    Gigabyte nVidia GeForce GTX 1660 Super OC 6GB
    Sound Card
    Onboard thingy
    Monitor(s) Displays
    5 x LG 25MS500-B - 1 x 24MK430H-B - 1 x Wacom Pro 22" Touch Screen Tablet
    Screen Resolution
    All over the place
    Hard Drives
    Too many to list.
    OS on Samsung 1TB 870 QVO SATA
    PSU
    Silverstone 1500
    Case
    NZXT Phantom 820 Full-Tower Case
    Cooling
    Noctua NH-D15 Elite Class Dual Tower CPU Cooler / 6 x EziDIY 120mm / 2 x Corsair 140mm somethings / 1 x 140mm Thermaltake something / 2 x 200mm Corsair.
    Keyboard
    Corsair K95 / Logitech diNovo Edge Wireless
    Mouse
    Logitech: G402 / G502 / Mx Masters / Mx Air Cordless
    Internet Speed
    2000/500Mbps
    Browser
    All sorts
    Antivirus
    Kaspersky Premium
    Other Info
    ㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤㅤ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
    TP-Link BE9300 WiFi 7 Bluetooth 5.4 (Archer TBE550E)
    TP-Link TX201 V1 2.5GB Lan

    Grandstream HT812 - VoIP
    ASUS DSL-AX82U - Mesh
    ASUS RT-AC68U - Mesh
    ASUS RT-BE88U Router

    Brother MFC-L2880DW Printer

    I’m on a horse.
  • Operating System
    Windows 11 Pro 25H2 Build 26200.8655
    Computer type
    Laptop
    Manufacturer/Model
    LENOVO Yoga 7 14IRL8 - 7i EVO OLED 14" Touchscreen i5 12 Core 16GB/512GB
    CPU
    Intel Core 12th Gen i5-1240P Processor (1.7 - 4.4GHz)
    Memory
    16GB LPDDR5 RAM
    Graphics card(s)
    Intel Iris Xe Graphics Processor
    Sound Card
    Optimized with Dolby Atmos®
    Screen Resolution
    QHD 2880 x 1800 OLED
    Hard Drives
    M.2 512GB
    Antivirus
    Defender / Malwarebytes
    Other Info
    …still on a horse.
Jorgen E said:
The search and index tool Everything will open a new world for You
Click to expand...
Does Everything index & search MSOffice Outlook pst & ost files?

The answer appears to be, No.
Outlook - voidtools forum

Jorgen E said:
Windows Search, as it's has always been slow and more or less useless
Click to expand...
I disagree.
I have found it useful and quick.
In addition to which, it can index and search in MSOffice Outlook pst/ost files.


Denis
 
Last edited:

My Computer

System One

  • OS
    Windows 11 Home x64 Version 25H2 Build 26200.8037
BirendraN said:
I installed 25H2 on 17 OCT 2025
My Build is Version 25H2 Build 26200.6901.
PC: Microsoft Surface 7 Snapdragon(R) X 12-core X1E80100 @ 3.40 GHz (3.42 GHz)
...
Click to expand...

Hi BirendranN,
you are not alone: I've got the exact same problem. Already filed a report in feedback hub 2 times, but no response. Have you got a solution? I ended up in disabling Windows search for now, otherwise CPU load keeps up at 100%...
 

My Computer

System One

  • OS
    Windows 11 Enterprise, 10.0.26220 Build 26220
    Computer type
    Tablet
    Manufacturer/Model
    Microsoft Corporation Surface_Pro_11th_Edition_2076
    CPU
    Snapdragon(R) X 12-core X1E80100 @ 3.40 GHz
    Memory
    16GB
bb901 said:
Hi BirendranN,
you are not alone: I've got the exact same problem. Already filed a report in feedback hub 2 times, but no response. Have you got a solution? I ended up in disabling Windows search for now, otherwise CPU load keeps up at 100%...
Click to expand...
No solution apart from using gpedit.msc if you have windows pro to prevent outlook indexing whilst retaining windows search. I posted to the feedback hub as well today. I also reinstalled office but no good. Is your system ARM too ?
 

My Computer

System One

  • OS
    windows 11
    Computer type
    Laptop
Yes...
1762193237943.webp
 

My Computer

System One

  • OS
    Windows 11 Enterprise, 10.0.26220 Build 26220
    Computer type
    Tablet
    Manufacturer/Model
    Microsoft Corporation Surface_Pro_11th_Edition_2076
    CPU
    Snapdragon(R) X 12-core X1E80100 @ 3.40 GHz
    Memory
    16GB
BirendraN said:
No solution apart from using gpedit.msc if you have windows pro to prevent outlook indexing whilst retaining windows search.
Click to expand...
Good point - did so, too.
 

My Computer

System One

  • OS
    Windows 11 Enterprise, 10.0.26220 Build 26220
    Computer type
    Tablet
    Manufacturer/Model
    Microsoft Corporation Surface_Pro_11th_Edition_2076
    CPU
    Snapdragon(R) X 12-core X1E80100 @ 3.40 GHz
    Memory
    16GB
Please post here anybody if Microsoft releases a solution
 

My Computer

System One

  • OS
    windows 11
    Computer type
    Laptop
Same problem here. I also have a device with an ARM processor. Set “AllowAppVSubsystems” to 0 did not solve the problem.
 

My Computer

System One

  • OS
    11
BirendraN said:
Please post here anybody if Microsoft releases a solution
Click to expand...
Did the latest Office Updates this morning, enabled Outlook Indexing back again and finally the problem seems to be solved.
 

My Computer

System One

  • OS
    Windows 11 Enterprise, 10.0.26220 Build 26220
    Computer type
    Tablet
    Manufacturer/Model
    Microsoft Corporation Surface_Pro_11th_Edition_2076
    CPU
    Snapdragon(R) X 12-core X1E80100 @ 3.40 GHz
    Memory
    16GB
bb901 said:
Did the latest Office Updates this morning, enabled Outlook Indexing back again and finally the problem seems to be solved.
Click to expand...
Thanks. Agree that updating (quite a lengthy process) does appear to have fixed the issue. No further event IDs 1000 in Event Log. Would have been nice if Microsoft acknowledge the issue in the Feedback Hub and in their update history.
 

My Computer

System One

  • OS
    windows 11
    Computer type
    Laptop
I have similar trouble with Outlook (classic) and e-mails in a local PST file since I upgraded from Windows 10 (not that trouble with Windows 10) to 11 in August 2025:
  • As soon as I start Outlook, Search Indexer is working for 10-30 minutes and lets the already completed search index approximately double to triple it's size. Next time the search index goes back to double size, it's size is changing massively every time I start Outlook.
  • Every time Office and Outlook get an update, the trouble has gone, but just for a few days after which it comes back.
  • My CPU ist not ARM, but AMD (but I found the same problem also on a PC with Intel CPU).
  • Outlook has currently version 2511 from monthly enterprise channel.
Could here also the App-V subsystems be the reason for the trouble?
 

My Computer

System One

  • OS
    Windows 11
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