How to Repair Outlook 365 in Windows 10

To repair classic Outlook that came with Microsoft 365 on Windows 10, close Outlook, right-click Start, select Apps and Features, select your Microsoft 365 or Office product, choose Modify, then pick Quick Repair and select Repair. If the problem comes back, run the same tool again with Online Repair. The repair fixes damaged program files. It does not fix a broken mail profile, a faulty add-in or a damaged data file, so this guide also covers those fixes, plus what to do if you use the new Outlook for Windows instead.

Applies to: classic Outlook for Microsoft 365 (and Outlook 2024, 2021, 2019 and 2016 where noted) on Windows 10, plus the new Outlook for Windows app. Checked against Microsoft Support on October 7, 2026.

Check which Outlook you have first

Windows 10 PCs can have two different Outlook apps, and they are repaired in different ways.

• Classic Outlook has a File tab at the top left. It is installed with Microsoft 365 or Office, so the Office repair tool, safe mode, profiles and data file repair in this guide all apply to it.
• New Outlook for Windows has a Settings button and shows Home, View and Help tabs instead of File. It is a separate app from the Microsoft Store, so jump to the new Outlook section below.

Microsoft’s guide What version of Outlook do I have? shows both layouts if you are unsure.

Before you repair: protect your mail

• Check your mail online. Sign in to your mailbox in a web browser. If messages are missing there too, the problem is with the account or the mail service, and repairing Outlook on your PC will not bring them back.
• Back up any .pst files. A .pst file (Outlook Data File) stores mail only on your PC, often for POP accounts or archives. Copy it to another drive while Outlook is closed. To see where your data files are, open classic Outlook and go to File > Account Settings > Account Settings, then open the Data Files tab.
• Have your sign-in details ready. You may need your Microsoft account or work or school password after a repair.

Repair Microsoft 365 (classic Outlook) in Windows 10

Microsoft describes the repair as finding and replacing corrupted Office program files; it works on the apps, not on your mailbox. It always covers the whole suite, so Word, Excel and the other apps are repaired too even if only Outlook misbehaves.

1. Close Outlook and the other Office apps. Save any open work in Word, Excel or PowerPoint first.
2. Right-click the Start button in the lower-left corner and select Apps and Features. The Settings app opens on the list of installed programs.
3. Select your Microsoft 365 or Office product in the list and select Modify.
4. Pick a repair type. In the window titled How would you like to repair your Office Programs, choose Quick Repair first. It is faster and only finds and replaces corrupted files.
5. Select Repair and follow the on-screen instructions. Leave the Office apps closed until the repair says it is finished.
6. Restart the PC if asked, then open Outlook and try whatever was failing before.
7. If the problem is still there, repeat steps 2 to 5 with Online Repair. Microsoft recommends Online Repair when you want to make sure everything gets fixed. It takes longer than Quick Repair.

Older Office installed from an MSI file: some volume-license and older Office versions show a Change your installation window instead. Select Repair, then Continue. Microsoft’s Repair an Office application page covers both installation types.

Alternative: start the repair from Control Panel

If the Settings route does not show Modify, use Control Panel instead.

1. Type control panel in the taskbar search box and open Control Panel.
2. Go to Programs > Programs and Features.
3. Right-click your Microsoft 365 or Office product and select Change. When the Office repair window appears, continue from step 4 above.

If repairing Office did not fix Outlook

When classic Outlook still crashes, freezes or will not open, work through these fixes in order. Each one targets a different cause.

1. Start Outlook in safe mode to test add-ins

Safe mode starts Outlook with add-ins turned off. Add-ins are small extensions from other programs, such as PDF tools or meeting plug-ins, and an outdated one is a common reason Outlook will not start.

1. Press Windows key + R, type Outlook.exe /safe and select OK. If Windows cannot find the command, use the full path to Outlook in your Office installation folder.
2. In the Choose Profiles box, keep the default profile and select OK. Enter your password if asked.
3. Look for the safe mode label at the top of the window and a caution icon on the Outlook taskbar button.

If Outlook works in safe mode, an add-in is the likely cause. If it still fails, skip to the profile fix below.

2. Turn off add-ins one at a time

1. In Outlook (safe mode is fine), select File > Options > Add-ins.
2. At the bottom, make sure Manage shows COM Add-ins, then select Go.
3. Note or screenshot which add-ins are checked, clear all the check boxes and select OK. Do not select Remove; you only want to disable them.
4. Select File > Exit, then start Outlook normally.
5. Turn the add-ins back on one at a time, restarting Outlook after each. When the problem returns, the last add-in you enabled is the culprit. Leave it off and check its maker for an update.

3. Repair your Outlook profile

A profile is the set of accounts and settings Outlook loads when it starts. The built-in repair can fix sending, receiving and connection problems.

1. In Outlook, select File > Account Settings > Account Settings.
2. On the Email tab, select your account and select Repair.
3. Follow the wizard, then restart Outlook.

Microsoft notes that Repair is not available in Outlook 2016 when it connects to an Exchange account.

4. Create a new Outlook profile

If Outlook will not open even in safe mode, the profile itself may be damaged. Creating a new one leaves the old profile in place, so you can switch back.

1. Open the profile picker: hold Shift while you start Outlook, or right-click Start, select Run, type Outlook.exe /profiles and press Enter. If Outlook is open, use File > Account Settings > Change Profile (Outlook restarts).
2. Select Options. If you want Outlook to ask which profile to use each time it starts, check the prompt option here.
3. Select New, type a name for the profile and select OK.
4. Add your email account when prompted, then pick the new profile in the Choose Profile list and select OK.

If Outlook starts normally with the new profile, the old one was corrupt. Back up your data before you delete the old profile, because removing it also deletes its offline copy of your mail.

5. Repair a damaged .pst or .ost data file

Classic Outlook includes the Inbox Repair tool (SCANPST.EXE) for local data files. It only fixes file damage; it does not connect to or check mail stored on an Exchange or Microsoft 365 server.

1. Exit Outlook. Make a copy of the .pst file you want to check.
2. Open SCANPST.EXE. Microsoft lists it under Program Files (x86), then Microsoft Office, root, Office16 for Outlook 2019 and 2016; on other installs, search File Explorer for SCANPST.EXE.
3. Select Browse, choose the .pst file, then select Start to scan it.
4. If errors are found, select Repair. The tool saves a .bak backup in the same folder unless you change the name or location in the backup box.
5. Open Outlook. Recovered items may appear in a Recovered Personal Folders or Lost and Found folder. You may need to run the tool more than once.

For an Exchange account, the local file is an .ost (an offline copy of the mailbox). Instead of repairing it, close Outlook and delete the .ost; Outlook rebuilds it from the server the next time it opens. Full details are in Microsoft’s Repair Outlook Data Files (.pst and .ost) guide.

6. Reset the navigation pane

If Outlook fails while loading folders, close it, press Windows key + R, type Outlook.exe /resetnavpane and select OK. This resets the folder pane on that PC only.

7. Install the latest Office updates

In classic Outlook, go to File > Office Account > Update Options > Update Now. If you do not see Update Now, select Enable Updates first. If only an About button appears, your organization manages updates, so contact your IT help desk. If you have been clearing stored data as well, see our guide to clearing the Outlook cache in Windows 10.

8. Run Microsoft’s automated troubleshooters

Microsoft’s Get Help app includes classic Outlook troubleshooters for common startup and profile setup problems. The startup troubleshooter needs Windows 10 or later and must run on the same PC as Outlook. These tools do not work with new Outlook. Start from Microsoft’s page Resolve Outlook for Windows issues with automated troubleshooting tools.

Fix the new Outlook for Windows

The new Outlook is installed from the Microsoft Store, not with the Office suite, so the Office repair above does not apply to it. Microsoft’s documented fixes are:

1. Force it to close and reopen. Right-click Start, select Task Manager, select Microsoft Outlook and choose End task. Close Task Manager and open Outlook again.
2. Uninstall it. Find new Outlook for Windows in the Start menu and choose Uninstall.
3. Reinstall it from the Microsoft Store. Open the Microsoft Store app, go to the Outlook listing and select Get (or Open if it is already installed). Windows 10 needs version 17763.0 or later. Add your accounts again if they do not appear automatically.

Still not working?

• Everyone at work has the same problem: it is probably a service issue. Your IT admin can check Microsoft 365 service health.
• Repair or Modify is greyed out or blocked: work and school PCs often restrict changes to Office. Ask your IT help desk to run the repair.
• Outlook 2016 or 2019 with a Microsoft 365 mailbox: Microsoft no longer supports these versions for connecting to Microsoft 365 services, so moving to a current version may be the real fix.
• Nothing above helped: uninstall and reinstall Office. Our guide to uninstalling Microsoft Office in Windows 10 covers the removal steps; then install Office again.

Frequently asked questions

Will repairing Outlook delete my emails?

The Office repair targets Outlook’s program files, not your messages, and mail kept in an online mailbox lives on the mail server rather than in the program. Local .pst files can hold mail that exists nowhere else, so back them up before any repair as a precaution.

Should I use Quick Repair or Online Repair?

Start with Quick Repair because it is faster. If the same problem returns, run Online Repair, which Microsoft recommends when you want to be sure everything is fixed.

Can I repair only Outlook and not the rest of Office?

Not when Outlook came with Microsoft 365 or an Office suite. The repair always covers the whole suite. Only a standalone copy of an app can be repaired on its own.

How do I know if an add-in is causing the problem?

Start Outlook with Outlook.exe /safe. If it works normally in safe mode, an add-in is very likely the cause. Disable add-ins and turn them back on one at a time to find it.

Does Microsoft 365 still work on Windows 10?

Yes, for now. Windows 10 support ended on October 14, 2025, but Microsoft will keep sending security updates for Microsoft 365 Apps on Windows 10 until October 10, 2028. New features stop at Version 2608, and Microsoft support may ask you to move to Windows 11 if a problem only happens on Windows 10. See Windows 10 end of support and Microsoft 365 Apps.

Does the Office repair fix the new Outlook?

No. The new Outlook is a separate Microsoft Store app. Close it with Task Manager, or uninstall it and reinstall it from the Microsoft Store.

Start with Quick Repair, and if Outlook still misbehaves, test it in safe mode before you move on to profiles and data files.

Related: how to configure Outlook in Windows 10.