How to Fix Microsoft Outlook Slow to Open on Windows

What Causes This?

Outlook usually opens slowly when something delays its startup sequence. The most common causes are faulty or overloaded add-ins, a damaged Outlook profile, oversized PST or OST data files, or background issues with Microsoft 365 syncing. In some cases, Windows startup load, antivirus scanning, or a stuck Outlook process can also make Outlook take much longer to launch.

Common Symptoms

• Outlook stays on the splash screen for a long time
• The window opens blank or shows “Loading Profile” for several minutes
• Outlook only opens quickly in Safe Mode
• The app freezes or becomes “Not Responding” during launch
• Email and folders load very slowly after Outlook finally opens

How to Fix It Manually

1. Make sure Outlook is fully closed

   1. Press Ctrl + Shift + Esc to open Task Manager.
   2. Look for Microsoft Outlook under the Processes tab.
   3. If it is still running, click it and choose End task.
   4. Also close related Office apps like Teams or Word if they are heavily using system resources.

2. Start Outlook in Safe Mode to check add-ins

   1. Press Windows + R to open Run.
   2. Type outlook.exe /safe and press Enter.
   3. If Outlook opens much faster in Safe Mode, an add-in is likely causing the delay.
   4. In Outlook, go to File > Options > Add-ins.
   5. At the bottom, next to Manage COM Add-ins, click Go.
   6. Uncheck all add-ins, click OK, then restart Outlook normally.
   7. Re-enable add-ins one at a time until you find the slow one.

3. Repair your Outlook data file

   1. Close Outlook.
   2. Open File Explorer and browse to one of these folders:
      • C:\Program Files\Microsoft Office\root\Office16
      • C:\Program Files (x86)\Microsoft Office\root\Office16
   3. Find and open SCANPST.EXE.
   4. Select your Outlook PST file, then click Start.
   5. If errors are found, choose Repair.
   6. If you use an Exchange, Microsoft 365, or IMAP account, rebuilding the OST file can also help:
      • Go to %localappdata%\Microsoft\Outlook
      • Rename the .ost file
      • Reopen Outlook so it creates a fresh copy

4. Create a new Outlook profile

   1. Press Windows + S, type Control Panel, and open it.
   2. Change View by to Large icons or Small icons.
   3. Click Mail (Microsoft Outlook).
   4. Select Show Profiles.
   5. Click Add, give the new profile a name, and set up your email account.
   6. Under When starting Microsoft Outlook, use this profile, choose Prompt for a profile to be used or set the new one as default.
   7. Open Outlook and test the new profile.

5. Update Office and Windows

   1. Open Outlook or another Office app.
   2. Go to File > Office Account > Update Options > Update Now.
   3. Then open Settings > Windows Update and click Check for updates.
   4. Restart your PC after updates finish.

6. Reduce startup and background load

   1. Open Task Manager with Ctrl + Shift + Esc.
   2. Go to the Startup apps tab.
   3. Disable non-essential apps that launch with Windows.
   4. Restart your PC and test Outlook again.
   5. If you use third-party antivirus, temporarily disable email scanning features and check whether Outlook opens faster.

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