Cannot Start Microsoft Outlook on Windows? Fix It

If Microsoft Outlook will not open on a Windows PC, the cause is often a stuck background process, a faulty add-in, a damaged navigation setting, or a problem with the Office installation. Work through these steps in order, starting with quick checks that do not change your mail or account settings; have your Windows sign-in and, if needed, email account password available.

What You’ll Need

Access to the Windows account where Outlook is installed.
Your email password or organization sign-in method, in case Outlook asks you to authenticate again.
A few minutes to restart the computer and test Outlook between steps.

Step-by-Step

Check for a hidden Outlook process. Press Ctrl+Shift+Esc to open Task Manager. In the Processes list, look for Microsoft Outlook or Outlook. If it is still running after you closed it, select it and choose End task. Do not end unrelated Office or Windows processes. Try opening Outlook again from the Start menu.
Restart Windows and check for a service issue. Save your work in other applications, then choose Start > Power > Restart. After signing in, try Outlook. If you use a work or school account, check whether your organization has reported an email service outage or sign-in problem. Avoid repeatedly entering your password if authentication is failing.
Try Outlook in Safe Mode. Press Windows+R, type outlook.exe /safe, and press Enter. If Windows says it cannot find the file, open Start, search for Outlook, and try the command again from the Run dialog; on some installations, the executable is not available through that command. If Outlook opens in Safe Mode, an add-in or customization may be responsible. Continue to the next step. If it does not open, skip to Step 5.
Disable add-ins if Safe Mode works. In Outlook, go to File > Options > Add-ins. At the bottom, next to Manage, select COM Add-ins, then choose Go. Note which boxes are selected, clear them, and select OK. Close Outlook and open it normally. If it now works, return to the same list and re-enable add-ins one at a time, restarting Outlook after each, to identify the one causing the failure. Leave a problematic add-in disabled or contact its provider or your IT team.
Reset the navigation pane. If Outlook does not open normally, close it and press Windows+R. Enter outlook.exe /resetnavpane and press Enter. This resets the navigation pane settings, such as the folder list arrangement; it does not delete messages. If the command is not recognized, search for Outlook in Start and use the installed app’s shortcut, or continue to repair Office.
Repair Microsoft 365 or Office. Close Office apps. Open Settings > Apps > Installed apps (called Apps & features in some Windows versions). Find Microsoft 365 or your Office installation, select the menu beside it, then choose Modify. If offered, try Quick Repair first and follow the prompts. Restart Windows and test Outlook. If the problem remains, repeat the process and choose Online Repair, if available. Online Repair may take longer and require internet access; it can also require you to sign in again.
Install pending updates. Open Settings > Windows Update and select Check for updates. Install applicable updates and restart. If Office apps open, use an Office app’s File > Account > Update Options > Update Now option when available. If no Office app opens, do not let this block the other troubleshooting steps.
Create a test Outlook profile. Try this if Outlook still will not start and the earlier steps have not helped. Close Outlook, search Windows for Control Panel, and open Mail or Mail (Microsoft Outlook). Select Show Profiles, then Add, and follow the prompts to create a profile. If available, set Outlook to prompt for a profile, then start Outlook and select the new one. Your messages may take time to sync. Keep the old profile until you have confirmed the new one works; do not delete data files as a test.

Common Mistakes

Deleting Outlook data files too soon. A local data file may contain cached or unsynced information. Do not delete or move PST or OST files as an initial fix. If you use a POP account or store mail only on the computer, get help before changing its data files.
Assuming Safe Mode fixes the cause. Safe Mode is a diagnostic test. If it works, identify the add-in or customization rather than relying on Safe Mode for normal use.
Running repairs while Office is open. Close Outlook and other Office apps first, and allow the repair to finish before restarting or interrupting the computer.
Removing an account or profile without checking sync. Some mail is stored online, but locally stored mail and settings may not be. Confirm that important messages are available elsewhere before removing profiles or accounts.

Tips

Change one thing at a time and test Outlook after each step. That makes it easier to spot the cause.
Write down the exact error message and when it appears. This is useful if you need help from your email provider or IT support.
If Outlook opens but repeatedly asks for a password, check the account sign-in method with your organization or email provider rather than sharing your password with anyone offering unsolicited help.
For a managed work or school computer, check with IT before creating profiles, changing add-ins, or running repairs. Organization policies can affect these options.

Troubleshooting

Outlook will not open in Safe Mode: Continue with an Office repair, then Windows and Office updates. If Outlook displays an error, record it exactly. If the app closes without a message, check whether other Office apps also fail; that may point to an Office installation or Windows issue rather than an Outlook-only problem.

The repair option is missing: You may have a different installation type or a managed device. Check Settings > Apps > Installed apps for the Office entry. If there is no Modify option, contact your administrator or use the installation support available through your organization.

A new profile does not help: Keep the original profile intact. Confirm that the account can sign in through your provider’s normal webmail page, if available, and ask your provider or IT team to check account access and service status. Do not treat webmail access as proof that all Outlook settings are correct.

Outlook opens, then freezes or crashes: Disable add-ins using the Safe Mode procedure, install updates, and retry Office repair. If the issue began after a recent add-in or Office change, tell support what changed and when.

Frequently Asked Questions

Will resetting the navigation pane delete my email?
No. The reset command restores navigation pane settings. It is not intended to delete messages or mail folders.

Can I use Outlook in Safe Mode permanently?
It is better as a diagnostic step. Safe Mode may disable add-ins and other customizations you normally use.

What if Outlook asks me to sign in after repair?
Sign in using the normal account method for your work, school, or personal email. If authentication fails, contact the account provider or your organization’s IT team.

Will creating a new profile erase my old messages?
Creating a profile does not itself require deleting the old one, but locally stored mail may not be available in a new profile until data is connected or imported. Keep the old profile and files until you confirm everything important is accessible.

Should I reinstall Office if these steps fail?
Try the available repair options first. If Outlook still cannot start, ask your IT administrator or Microsoft support to review the exact error and installation before reinstalling, especially on a managed computer.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

More in this bed

The whole Tech How-To bed →