No Ticket Needed

Appearance

8 min fix 10 min read Recently reviewedBeginner

By , IT support technician

Quick Answer

Hold the Ctrl key on your keyboard while clicking the Outlook icon. When asked if you want to start in Safe Mode, click Yes to bypass corrupted add-ins.

How to Fix Outlook Not Opening or Crashing on Startup ​

Applies to: Microsoft Outlook (Microsoft 365, Outlook 2021, New Outlook for Windows), Windows 10, Windows 11
Article Type: Troubleshooting
Last Updated: 2026-06-17

Summary ​

This article covers what to do when Outlook refuses to open — whether it crashes immediately after clicking the icon, gets stuck on the "Loading Profile…" splash screen, shows a brief flash then closes, or displays a "Cannot start Microsoft Outlook" error. These steps address the most common causes and require no admin rights.

Prerequisites ​

  • A working internet connection (verify by opening a web page in your browser).
  • Close all other Office apps (Word, Excel, PowerPoint) before attempting repairs — some steps restart shared Office components.

Instructions ​

1. Check for a Stuck Outlook Process ​

Outlook may already be running invisibly in the background. Windows prevents a second instance from launching, so clicking the icon does nothing.

  1. Press Ctrl + Shift + Esc to open Task Manager.
  2. Look through the list for Microsoft Outlook. It may appear under Apps or under Background processes.
  3. If you find it, click it and select End task.
  4. If you see multiple Outlook entries, end each one.
  5. Wait 10 seconds, then try launching Outlook again from the Start menu or taskbar.
  6. If Outlook opens normally, the issue was a stuck background process — a one-time glitch. If it still does not open, continue to Step 2.

2. Start Outlook in Safe Mode ​

Safe Mode launches Outlook with all add-ins disabled, custom toolbar settings ignored, and the Reading Pane turned off. If Outlook opens successfully in Safe Mode, the problem is an add-in or a customization — not Outlook itself.

  1. Press Win + R to open the Run dialog.
  2. Type outlook.exe /safe and press Enter.
  3. If prompted to choose a profile, select your default profile and click OK.
  4. Outlook opens with [Safe Mode] in the title bar and a simplified interface.
  5. If Outlook opens in Safe Mode: The crash is caused by an add-in or customization. Continue to Step 3 to isolate the problem add-in, then Step 4 to reset the Navigation Pane if needed.
  6. If Outlook still crashes in Safe Mode: The problem is deeper — skip to Step 5 to repair the Outlook data file.

3. Identify and Disable the Problem Add-In ​

Add-ins from antivirus software, CRM tools, PDF converters, and browser extensions are the most frequent cause of Outlook startup crashes.

  1. With Outlook open in Safe Mode (from Step 2), go to File > Options > Add-ins.
  2. At the bottom of the window, next to Manage, select COM Add-ins and click Go.
  3. You will see a list of all installed add-ins with checkboxes.
  4. Uncheck all add-ins and click OK.
  5. Close Outlook, then reopen it normally (not in Safe Mode) — from the Start menu or taskbar.
  6. If Outlook opens without crashing, an add-in was the cause.
  7. To find which one: go back to File > Options > Add-ins > COM Add-ins and re-enable add-ins one at a time, restarting Outlook after each, until the crash returns. The last add-in you enabled is the culprit.
  8. Leave the problem add-in disabled. If it is required for your work (e.g., a company CRM tool), ask IT for an updated version — give them the add-in's exact name from the COM Add-ins list and your Outlook version from File > Office Account.

4. Reset the Navigation Pane ​

A corrupted Navigation Pane configuration file can cause Outlook to crash on startup. Resetting it forces Outlook to rebuild the file.

  1. Close Outlook completely (end the process in Task Manager if needed).
  2. Press Win + R to open the Run dialog.
  3. Type outlook.exe /resetnavpane and press Enter.
  4. Outlook should open normally. Your folder list and favorites will be rebuilt automatically — no emails are deleted.
  5. If Outlook still crashes, continue to Step 5.

5. Repair the Outlook Data File (ScanPST) ​

Outlook stores a local copy of your mailbox in a data file (OST or PST). If this file becomes corrupted — due to a crash, power loss, or disk error — Outlook cannot read it and refuses to open.

  1. Close Outlook completely.
  2. Open File Explorer and navigate to the ScanPST tool. The location depends on your Office installation:
    • Microsoft 365 / Office 2021 (64-bit): C:\Program Files\Microsoft Office\root\Office16\SCANPST.EXE
    • Microsoft 365 / Office 2021 (32-bit): C:\Program Files (x86)\Microsoft Office\root\Office16\SCANPST.EXE
  3. Double-click SCANPST.EXE to launch it.
  4. Click Browse and navigate to your Outlook data file. The default location is:
    • C:\Users\[YourUsername]\AppData\Local\Microsoft\Outlook\ (for OST files)
    • C:\Users\[YourUsername]\Documents\Outlook Files\ (for PST files)
  5. Select the .ost or .pst file and click Start.
  6. If errors are found, check the box Make backup of scanned file before repairing and click Repair.
  7. Wait for the repair to complete, then try opening Outlook normally.
  8. If ScanPST reports no errors or the repair does not help, continue to Step 6.

6. Delete and Rebuild the Local Data File ​

If ScanPST cannot repair the file, or the corruption is severe, you can delete the local cache and let Outlook rebuild it from the server. This works because your emails are stored on the Microsoft 365 server — the local file is a copy.

  1. Close Outlook completely.
  2. Press Win + R, type %localappdata%\Microsoft\Outlook\ and press Enter.
  3. Find the .ost file for your account (it is usually named after your email address).
  4. Rename the file by adding .old to the end (e.g., [email protected]). Do not delete it — renaming it keeps a backup.
  5. Open Outlook. It will create a new OST file and re-download your mailbox from the server.
  6. Outlook may take several minutes to fully re-sync. Leave it running and connected to the internet.

7. Repair Your Office Installation ​

If Outlook still crashes after addressing add-ins and the data file, the Outlook program files themselves may be damaged.

  1. Close Outlook completely.
  2. Press the Start key, type Installed Apps, and press Enter.
  3. Search for Microsoft 365 (or Office).
  4. Click the … (three dots) next to it and select Modify.
  5. Select Quick Repair and click Repair. This takes 5–10 minutes and does not require internet.
  6. Open Outlook and test. If the crash continues, repeat the process and select Online Repair instead. Online Repair takes 15–30 minutes, requires internet, and is more thorough — it redownloads Office components.

8. Create a New Outlook Profile ​

If none of the above steps resolve the crash, the Outlook profile itself may be corrupted. Creating a new profile forces Outlook to start with a completely fresh configuration.

  1. Close Outlook completely.
  2. Press Win + R, type control, and press Enter to open Control Panel.
  3. Search for Mail and open Mail (Microsoft Outlook).
  4. Click Show Profiles.
  5. Click Add and enter a name for the new profile (e.g., NewProfile).
  6. Follow the prompts to sign in with your work email address.
  7. Once the profile is created, select Always use this profile and choose the new profile from the drop-down.
  8. Click OK and open Outlook. It will create a new data file and re-download your mailbox from the server.
  9. If the new profile works, you can delete the old profile from the same Show Profiles screen.

9. Try the New Outlook for Windows ​

If Classic Outlook continues to crash and you need email access immediately, the New Outlook for Windows uses a different engine and is not affected by profile corruption, add-in conflicts, or OST file issues.

  1. Press the Start key, type New Outlook, and press Enter.
  2. If it is available on your machine, it opens as a separate app.
  3. Sign in with your work email address.
  4. Use New Outlook as a temporary workaround while IT investigates the Classic Outlook crash.

10. When to Contact IT ​

Three answers let IT skip everything you have already ruled out: whether Outlook also crashes in Safe Mode, whether a brand-new profile behaved any differently, and the exact error text shown when it closes. Put those in the ticket.

Contact your IT helpdesk if:

  • Outlook crashes in Safe Mode and after a full Online Repair — the issue may require a reinstallation or account-level fix that needs admin access.
  • Creating a new Outlook profile did not resolve the crash.
  • You cannot find the ScanPST tool or do not have permission to access the Outlook data file folders.
  • The crash started immediately after an IT-deployed software update or policy change.
  • You see error messages referencing MAPI, Exchange, or RPC — these typically indicate a server-side configuration issue.
  • Multiple colleagues are experiencing the same crash at the same time — this suggests a server-side or network problem.

Troubleshooting ​

DANGER

If Outlook opens in Safe Mode but crashes when opened normally, the cause is almost certainly an add-in. Focus on Step 3. If Outlook crashes even in Safe Mode, focus on the data file (Steps 5–6), Office Repair (Step 7), and creating a new profile (Step 8).

Symptom / ErrorPotential CauseSolution
Clicking Outlook does nothing — no window appearsStuck background processEnd the Outlook process in Task Manager (Step 1).
"Cannot start Microsoft Outlook. Cannot open the Outlook window."Corrupted Navigation Pane or profileReset the Navigation Pane (Step 4). If that fails, create a new profile (Step 8).
"The set of folders cannot be opened."Corrupted OST/PST data fileRun ScanPST (Step 5) or rebuild the data file (Step 6).
Outlook shows splash screen then closesAdd-in crash during startupStart in Safe Mode (Step 2) and disable add-ins (Step 3).
Outlook crashes after a Windows or Office updateCorrupted Office program filesRun Online Repair (Step 7).
Outlook crashes only when opening .msg or .ics filesFile association conflictRepair Office (Step 7) to restore correct file associations.
"Your mailbox has been temporarily moved to Microsoft Exchange server"Profile migration issueCreate a new Outlook profile (Step 8).
Crash with "AppCrash" or "OUTLOOK.EXE has stopped working"Corrupted add-in or data fileSafe Mode test (Step 2) → add-in isolation (Step 3) → data file repair (Step 5).