Classic Outlook is crashing and opening in Safe Mode. The faulting module is MSVCP140.dll. Two separate bugs can cause this, and both showed up in early 2026.

This post covers the Teams Meeting Add-in conflict (MSVCP140.dll) and the PST file locking crash introduced by the January 2026 Windows update.

Symptoms

You'll see one or more of these:

  • Outlook crashes on launch and restarts in Safe Mode
  • Event Viewer shows: Faulting module name: MSVCP140.dll / Faulting application: OUTLOOK.EXE
  • Outlook hangs at "Loading Profile"
  • Sent items go missing or emails re-download
  • Outlook freezes when accessing files from OneDrive or Dropbox

Why It's Crashing

There are two separate causes that look the same.

Cause 1: Teams Meeting Add-in (March 2026)

Teams Meeting Add-in build 1.26.02603, released around March 12, 2026, is incompatible with older Office builds. It tries to load MSVCP140.dll version 14.32.31332.0, which ships with Outlook builds 2402 (Build 17328.20142) or older. The version mismatch crashes Outlook at startup.

Cause 2: PST File Locking (January 2026)

The January 13, 2026 Patch Tuesday updates changed how Windows locks files. When Outlook stores PST files in a cloud-synced folder like OneDrive or Dropbox, the new locking behavior conflicts with how sync clients track file changes. Outlook can't write to the PST and crashes.

Affected Versions

Teams Add-in cause:

  • Classic Outlook builds 2402 (Build 17328.20142) and older
  • Any Windows version

PST locking cause:

  • Windows 11: versions 25H2, 24H2, 23H2
  • Windows 10: version 22H2
  • Outlook with PST files stored in OneDrive, Dropbox, or any sync folder

How to Fix It

Step 1: Update Microsoft Teams

This fixes the MSVCP140.dll crash from the Teams Add-in.

  1. Open Microsoft Teams.
  2. Click your profile picture in the top right.
  3. Select Check for updates.
  4. Wait for Teams to update, then restart it.
  5. Restart Outlook.

You need Teams version 26058.712.4527.9297 or newer.

Step 2: Update Microsoft Office

This brings your Outlook build up to date, fixing the MSVCP140.dll incompatibility.

  1. Open Word or Excel.
  2. Click File > Account.
  3. Click Update Options > Update Now.
  4. Restart Outlook after the update completes.

Step 3: Install the Emergency Windows Update

These updates fix the file locking issue that crashes Outlook when PST files are stored in cloud folders. Install the one that matches your OS:

  • Windows 11 25H2 / 24H2: install KB5078127
  • Windows 11 23H2: install KB5078132
  • Windows 10 22H2: install KB5078129

To install:

  1. Open Settings > Windows Update.
  2. Click Check for updates.
  3. Install the applicable update and restart.

Step 4: Move PST Files Out of Cloud Folders

If you can't install updates immediately, this stops the file locking conflict.

  1. Close Outlook.
  2. Open Control Panel > Mail > Data Files.
  3. Find any PST files stored inside OneDrive or Dropbox folders.
  4. Move them to a local path such as C:\OutlookData\.
  5. Update the Mail settings to point to the new location.

Step 5: Remove the Problematic Windows Update

If crashes started right after January 13, 2026 and you haven't been able to install the fix update:

  1. Go to Settings > Windows Update > Update history.
  2. Click Uninstall updates.
  3. Find KB5074109 (Windows 11) or KB5073724 (Windows 10).
  4. Uninstall and restart.
  5. Pause updates for 7 days to prevent reinstall until the fix update is available.

Classic Outlook crashing in your office? Rain City Techworks provides managed IT support for businesses in the Seattle-Tacoma area. Get in touch if your team needs help.