Why Is Outlook Not Opening? 7 Fixes That Work

Outlook fails to open most often because a corrupt profile or data file (.ost/.pst) is blocking startup, an incompatible add-in is crashing the app at launch, or an incomplete update left the installation in a broken state. All three are fixable within a few minutes on Windows or Mac.

7 Reasons Outlook Is Not Opening (and How to Fix Each)

Work through these in order — the first two fixes resolve the vast majority of Outlook launch failures without uninstalling anything.

Fix 1: Force-Quit and Restart in Safe Mode (30 Seconds)

Before anything else, check whether Outlook is already running silently in the background. Open Task Manager (Ctrl+Shift+Esc on Windows), look for "OUTLOOK.EXE" in the Processes tab, right-click it, and choose End Task. Then wait 10 seconds and relaunch Outlook normally.

If it still hangs, launch Outlook in Safe Mode -- this loads the app with all add-ins disabled:

1. Press Windows key + R to open the Run dialog.
2. Type outlook.exe /safe and press Enter.

If Outlook opens in Safe Mode, a faulty add-in is the cause. Skip to Fix 3 to identify which one.

"Launching Outlook with the /safe switch disables all COM add-ins and starts the application in a reduced-functionality state. This is the fastest way to determine whether a third-party add-in is responsible for a startup failure." -- Microsoft Support, Start Outlook in Safe Mode.

Fix 2: Repair the Outlook Data File (OST/PST)

If Safe Mode did not help -- or Outlook crashes immediately before reaching Safe Mode -- the most likely culprit is a corrupt local data file.

For IMAP / Microsoft 365 accounts (OST file):
1. Close Outlook completely (Task Manager if needed).
2. Navigate to C:\Users\[YourName]\AppData\Local\Microsoft\Outlook\.
3. Rename the .ost file to .ost.bak (or delete it -- it will regenerate from the server).
4. Reopen Outlook. It will rebuild the OST file from your server data. This can take several minutes.

For POP accounts (PST file) -- use the Inbox Repair Tool (SCANPST):
1. Close Outlook.
2. Find SCANPST.EXE in C:\Program Files\Microsoft Office\root\Office16\ (version number may vary).
3. Open SCANPST, browse to your .pst file, click Start, and let it repair any errors.
4. Reopen Outlook.

Fix 3: Disable All Add-Ins and Re-Enable One by One

If Outlook opened in Safe Mode (Fix 1), an add-in is responsible. Here is how to find which one:

1. While in Safe Mode, go to File > Options > Add-ins.
2. At the bottom, set the "Manage" dropdown to "COM Add-ins" and click Go.
3. Uncheck all add-ins and click OK.
4. Close Outlook and reopen it normally.
5. If Outlook opens, re-enable one add-in at a time (repeating steps 1-4) until the crash returns -- that add-in is the culprit.

Common problematic add-ins: Zoom, Teams Meeting Add-in, Adobe Sign, antivirus email scanner plugins.

Fix 4: Run Office Repair

A failed or incomplete Office update can leave Outlook's installation in a partially broken state. Run the built-in repair:

1. Open Settings > Apps > Installed Apps (Windows 11) or Control Panel > Programs and Features (Windows 10).
2. Find Microsoft 365 or Microsoft Office, click the three dots or right-click, and choose Modify.
3. Choose Quick Repair first (no internet required). If that fails, run Online Repair (reinstalls Office files from Microsoft's servers).

This repair process typically takes 5-20 minutes and fixes corrupted installation files.

Fix 5: Delete the Outlook Profile and Create a New One

A corrupt Outlook profile (not your email account -- the Windows profile Outlook uses to store settings) can prevent launch even with a healthy installation.

1. Open Control Panel > Mail (Microsoft Outlook) -- type "Mail" in the Windows search bar.
2. Click Show Profiles.
3. Note the existing profile name, then click Add to create a new profile.
4. Set it up with your email account (the wizard will walk you through this).
5. Set the new profile as the default and launch Outlook.

If Outlook launches successfully with the new profile, the old one was corrupt. You can delete the old profile once everything is confirmed working.

Fix 6: Check Outlook's Status on Another Device

If you are using Microsoft 365 (Exchange-hosted email) and Outlook is stuck at the loading screen even in Safe Mode, the issue may not be local. Check:

• Microsoft 365 Service Health: Log in to admin.microsoft.com and look at Health > Service Status. An active Exchange Online incident can block Outlook from loading.
• Open Outlook on your phone or web browser (outlook.com or your organization's OWA URL). If email loads there but not in the desktop app, the server is fine and the problem is local.

Fix 7: Reinstall Microsoft Office

If all prior fixes failed, a clean reinstall is the definitive solution:

1. Download and run the Microsoft Support and Recovery Assistant (SaRA) from support.microsoft.com -- this tool handles uninstalling Office more cleanly than manual removal.
2. After uninstall and restart, reinstall Office from office.com or your organization's software portal.

This preserves your Windows user profile and Outlook profile data -- it only reinstalls the Office application files.

Our Pick: USB flash drives and external drives -- back up your Outlook PST file before running repairs

Outlook Not Opening on Mac

On a Mac, the most effective fixes differ slightly:

1. Force-quit: Open Activity Monitor (Applications > Utilities), find Microsoft Outlook, and force-quit.
2. Delete the preference file: Navigate to ~/Library/Group Containers/UBF8T346G9.Office/ and delete the com.microsoft.Outlook.plist file. Outlook recreates it on next launch.
3. Rebuild the database: Hold Option while clicking the Outlook icon in the Dock to open the Microsoft Database Utility, then click Rebuild.
4. Update Outlook: Open Microsoft AutoUpdate (Help > Check for Updates). Running an outdated Outlook version on an updated macOS is a frequent source of launch failures.

Related Articles on WhyIsMy.org

• Why Is My Outlook Not Receiving Emails?
• Why Is My Outlook Search Not Working?
• Why Is My Outlook Calendar Not Syncing?
• Why Is My Office 365 So Slow?

Also Read: Find USB drives, laptop accessories, and PC troubleshooting tools on Amazon

In Short

Outlook not opening is almost always caused by a corrupt OST/PST data file, a broken add-in, or a damaged Office installation. Start with Safe Mode (/safe switch) to test add-ins; if Outlook opens there, disable add-ins one by one. If Safe Mode also fails, rename or delete the OST file (IMAP accounts) or run SCANPST (POP accounts). Run Office Quick Repair next. If all else fails, delete the Outlook profile and create a new one, or use Microsoft's SaRA tool for a clean reinstall.

What You Also May Want To Know

Why does Outlook keep crashing on startup but Task Manager shows it running?

Outlook may be stuck in a crash-restart loop -- it launches, crashes immediately, and Windows is auto-restarting it. Use Task Manager to end all OUTLOOK.EXE processes, then use the /safe switch to launch in Safe Mode and break the loop.

How do I find where my PST file is located?

In Outlook, go to File > Account Settings > Account Settings > Data Files tab. The file path column shows the exact location. If Outlook will not open, check the default location: C:\Users\[YourName]\Documents\Outlook Files\ or C:\Users\[YourName]\AppData\Local\Microsoft\Outlook\.

Can Windows updates break Outlook?

Yes -- occasionally a Windows update conflicts with a specific Outlook version, particularly when the update modifies system components Outlook relies on. If Outlook stopped working immediately after a Windows update, check Microsoft's Known Issues page for your Office version and consider rolling back the specific update via Windows Update history.

Why does Outlook get stuck at the loading screen with "processing"?

This usually means Outlook is connecting to an Exchange server and waiting for a response that is not coming. Common causes: Exchange server maintenance, VPN not connected (for corporate accounts requiring VPN), or a corrupt autodiscover entry. Try disconnecting from the network, opening Outlook (it will load in offline mode), then reconnecting.

What is the SCANPST tool and is it safe to use?

SCANPST (the Inbox Repair Tool) is Microsoft's official utility for repairing corrupt PST files, included with every Windows Office installation. It creates a backup of the original file before making any changes (look for a .BAK file in the same folder). SCANPST cannot repair every type of corruption but resolves the majority of PST-related launch failures.

Reviewed and Updated on June 30, 2026 by Adelinda Manna