Fix: Microsoft Teams Meeting Add-in Causing Outlook to Crash

One of our customers recently reached out after Outlook started crashing every time they opened it. The culprit turned out to be the Microsoft Teams Meeting Add-in, a tool they relied on daily to schedule Teams meetings directly from Outlook. With the add-in enabled, Outlook would crash immediately, and the only way to get it open was in Safe Mode. They had already tried clearing the cache based on an AI suggestion, but it made no difference. After investigating, we found this is a widespread issue affecting thousands of Classic Outlook users worldwide, and Microsoft has since acknowledged it. Here is what we found and how to fix it.

Symptoms

When the Microsoft Teams Meeting Add-in is enabled, Outlook crashes immediately on launch. Users may experience the following:

Outlook crashes immediately or shortly after opening when the Teams Meeting Add-in is active. The only way to open Outlook is in Safe Mode, which automatically disables the add-in.

• Outlook can only be opened in Safe Mode (hold Ctrl while launching, or run outlook.exe /safe).
• The Teams Meeting button is unavailable because the add-in must remain disabled to keep Outlook running.
• Users cannot schedule Microsoft Teams meetings from within Outlook.
• Windows Event Viewer may show Event ID 1000 with exception code 0xc0000005 (access violation) and faulting module MSVCP140.dll.

The add-in appears in File > Options > Add-ins > COM Add-ins as Microsoft Teams Meeting Add-in for Microsoft Office.

Affected Software

• Application: Microsoft Outlook (Classic) - Microsoft 365, Office 2021, Office 2019, Office 2016
• Platform: Windows 10 / Windows 11 (both 32-bit and 64-bit installations)
• Related Services: Microsoft Teams Meeting Add-in version 1.26.02603
• Not affected: New Outlook for Windows, Outlook on the web, Outlook mobile

Cause

This is a known Microsoft issue tracked under incident EX1254044, affecting Classic Outlook installations from around March 12, 2026 onwards.

The root cause is a compatibility conflict between Teams Meeting Add-in version 1.26.02603 and an outdated Visual C++ runtime DLL (MSVCP140.dll version 14.32.31332.0) bundled with older Office builds. The newer add-in triggers a memory access violation during initialisation, crashing Outlook before it fully loads.

Outlook builds at or below Version 2402 (Build 17328.20142) in the Current Channel are affected.

Resolution

Work through these steps in order, testing after each one.

Step 1: Update Microsoft Office (Primary Fix)

Since Outlook itself crashes, use another Office app to trigger the update:

1. Open Microsoft Word (or Excel).
2. Go to File > Account > Update Options > Update Now.
3. Wait for the update to download and install.
4. Close Word and open Outlook normally (not in Safe Mode).

Microsoft confirms that up-to-date Office builds resolve this issue.

Step 2: Update the Visual C++ Redistributable

If Office updates are not immediately available, updating the underlying runtime can resolve the crash:

1. Download the latest Microsoft Visual C++ 2015-2022 Redistributable (version 14.40 or higher) from Microsoft.
2. Install the x64 version. If running 32-bit Office, also install the x86 version.
3. Restart your computer.
4. Open Outlook normally.

Step 3: Disable the Add-in Temporarily (Workaround)

If you need Outlook working immediately while waiting for updates:

1. Hold Ctrl and click the Outlook shortcut. Select Yes to start in Safe Mode.
2. Go to File > Options > Add-ins.
3. At the bottom, ensure COM Add-ins is selected in the Manage dropdown and click Go.
4. Uncheck Microsoft Teams Meeting Add-in for Microsoft Office.
5. Click OK and restart Outlook normally.

You can schedule Teams meetings directly from the Teams app while the add-in is disabled. Re-enable the add-in after applying Office updates.

Step 4: Clear Registry Resiliency Keys

If Outlook has flagged the Teams add-in as crashed, you may need to clear the resiliency entries:

1. Close Outlook completely.
2. Press Win + R, type regedit, and press Enter.
3. Navigate to:
   HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Resiliency\DisabledItems
4. Delete any entries that reference TeamsAddin or Microsoft.Teams.AddinLoader.
5. Close Registry Editor and open Outlook normally.

Step 5: Re-register the Add-in DLL

1. Close Outlook and Teams.
2. Open File Explorer and navigate to %LocalAppData%\Microsoft\TeamsMeetingAddin.
3. Open the subfolder with the highest version number.
4. Open Command Prompt as Administrator and run:
   For 64-bit Office: regsvr32 /n /i:user "[path]\x64\Microsoft.Teams.AddinLoader.dll"
   For 32-bit Office: regsvr32 /n /i:user "[path]\x86\Microsoft.Teams.AddinLoader.dll"
5. Restart Teams (sign out and back in), then restart Outlook.

Note: Do not run Outlook as Administrator, as this can prevent the add-in from loading.

Step 6: Repair Microsoft Office

1. Open Settings > Apps > Installed apps.
2. Find Microsoft 365 Apps (or Microsoft Office), click the three-dot menu, and select Modify.
3. Select Online Repair and follow the prompts.
4. After the repair completes, restart your computer and open Outlook.

For IT Administrators: Disable via Registry at Scale

To temporarily disable the add-in across multiple machines via PowerShell:

Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\Outlook\Addins\TeamsAddin.FastConnect" -Name LoadBehavior -Value 2

To re-enable after updates are deployed:

Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\Outlook\Addins\TeamsAddin.FastConnect" -Name LoadBehavior -Value 3

LoadBehavior values: 3 = load at startup (enabled), 2 = do not load at startup (disabled).

Verify the Fix

1. Open Outlook normally (not in Safe Mode).
2. Create a new meeting and confirm the Teams Meeting button appears in the ribbon.
3. Click the button to confirm it adds Teams meeting details to the invite.

Important Notes

• This issue is tracked by Microsoft under incident EX1254044. A fix has been released via Office updates.
• Microsoft Teams version 26058.712.4527.9297 (deploying from March 30, 2026) also includes a fix on the Teams side.
• The Teams Meeting Add-in requires both Teams and Outlook to be running the same architecture (both 32-bit or both 64-bit). Mismatched installations can cause separate issues.
• New Outlook for Windows is not affected by this issue and does not use the COM add-in.

Related Resources

• How to Add a Shared Mailbox in Outlook for Mac
• Microsoft: Classic Outlook crashes and opens in Safe Mode starting March 12, 2026
• Microsoft: Resolve issues with the Teams Meeting add-in for Outlook
• Microsoft: Understanding the Teams Meeting Add-in for Outlook

If you need help resolving Outlook or Teams add-in issues, get in touch with our team.