Outlook won't open. Solutions for "Cannot start Microsoft Outlook" error.

This guide explains the most common reasons why Outlook is not opening and provides clear, practical solutions to get it running again. The fixes work for any version, from Microsoft 365 to Outlook 2016.

A few articles ago we discussed what can be done when Outlook is freezing and not responding. Today, let's see how you can fix and prevent an even worse scenario when your Outlook does not open at all.

Why won't Outlook open?

The main symptom of this problem is obvious and easily recognizable: you click Outlook's icon, an hourglass appears and is hanging for a while, and then you get the "Cannot start Microsoft Outlook" error.

Outlook usually fails to start when something prevents it from loading your profile or data files. Typical causes include:

  • A damaged Outlook profile
  • Corrupted PST data file
  • A broken navigation pane configuration file
  • Outlook running invisibly in the background
  • Issues with the Outlook installation
  • Conflicts with third-party add-ins
  • Outdated versions of Outlook or Windows

Whatever the reason is, the outcome is the same - you cannot open the app because of this error: "Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened." Cannot start Microsoft Outlook. Cannot open the Outlook window.

How to resolve Outlook not opening problems

Now that you know what causes issues on Outlook startup, let's see how we can get them fixed. Below you will find the troubleshooting steps for the most common problems that prevent Outlook from opening, listed in order of frequency and efficiency.

Fix 1. Check if Outlook is already running

Before trying anything else, confirm that no Outlook processes are running in the background, preventing the app from starting anew.

  1. Press Ctrl + Shift + Esc to open Task Manager. Or right-click the taskbar and select Task Manager.
  2. Under Processes, look for Outlook items.
  3. If you see any, right-click it and choose End task.
  4. Try launching Outlook again.

If Outlook crashed silently earlier, this simple step often brings it back. End Outlook processes running in the background.

Fix 2: Start Outlook in Safe mode

Starting Outlook in safe mode actually means loading the app without any add-ins or custom settings. It's a quick way to check if a faulty plug-in or customization is interfering when Outlook tries to open.

To run Outlook in safe mode, click on its icon in the Start menu or Windows taskbar while holding the Ctrl key. In a pop-up window that appears, click Yes to confirm. Start Outlook in Safe mode.

Another way is to press Win + R to open the Run dialog box and enter this command: outlook /safe. If prompted, select your default Outlook profile and click OK to open it.

If Outlook starts fine in safe mode, one of your add-ins is likely to be the problem. Try to disable the add-ins one at a time to detect which one is causing the issue.

Fix 3: Install latest Outlook updates

Outdated builds of Outlook can sometimes cause startup issues, especially if a recent patch addressed a bug that affects how the app loads. A quick update may be all you need to get Outlook working again without further troubleshooting.

For detailed information, see how to update Outlook.

Also, keep in mind that support for Office 2016 and Office 2019 clients connecting to Microsoft 365 services ended in 2023. Microsoft has stated that these versions won't be intentionally blocked, but they are no longer tested with new Microsoft 365 services. As a result, users may encounter unpredictable connection problems, reduced performance, or features that no longer work as expected.

Fix 4. Reset Navigation Pane configuration file

The Navigation pane (the left-hand panel where you access Mail, Calendar, People, and Tasks) relies on a small XML file that stores its settings. When this file becomes corrupted, Outlook may fail to start. A noticeable sign of corruption is when the file shows a size of 0 KB in its folder. No one knows the exact reason why this happens, but all versions of Outlook from 2010 to Microsoft 365 may be affected.

Resetting the file usually resolves the problem without affecting your mailbox data. Here's how to do it:

  1. Press Win + R to open the Run
  2. Type the following command: outlook.exe /resetnavpane
  3. Press Enter or click OK.
Reset the Navigation Pane configuration file.

This command resets the navigation pane settings for your default Outlook profile if you have more than one. If no default profile is set, Outlook is expected to prompt you to choose one before the reset takes place.

Note. For the commend to work, be sure to type a space between outlook.exe and /resetnavpane.

Delete Navigation pane file

If the reset command doesn't fix the issue, you can delete the XML file. Outlook will recreate it automatically the next time it starts.

  1. Open the folder that contains the navigation pane file. For this, you can either:
    • Go to:
      C:\Users\<username>\AppData\Roaming\Microsoft\Outlook\profile_name.xml
    • Quickly access it by entering this path in File Explorer:
      %appdata%\Microsoft\Outlook
  2. Locate the .xml file that has the same name as your Outlook profile and delete it.
Delete the Navigation pane settings file.

Note.Try the reset command first. Deleting the XML file is the last resort if other options don't work.

Fix 5. Repair Outlook data file (.pst)

A damaged PST file is a frequent reason Outlook won't launch. Corruption can occur after an interrupted update, a system crash, or issues with your drive. When the data file can't be read properly, Outlook may stop at startup.

Microsoft provides a built-in tool called SCANPST.EXE that can diagnose and repair problems with .pst and .ost files. Follow the instructions in the Repairing Outlook Data Files guide, let the tool run a full scan, and complete the repair process. Once it's done, try opening Outlook again. If it launches normally, you are all set and do need the rest of the troubleshooting steps :)

Tip. If your account uses an .ost file (Exchange or IMAP), you can delete the OST instead of repairing it. Outlook will recreate it automatically the next time it starts.

Fix 6. Change the default Outlook account

If you have more than one account set up in Outlook, startup issues can occur when the program can't access the default PST file. The file itself may be perfectly fine, just temporarily unavailable. For example, when the file is stored on a network share or in a cloud folder like OneDrive that can't be reached at the moment. It can also happen if the PST file was moved or deleted. When Outlook can't locate the primary data file, it may refuse to open.

If this sounds like your situation, switching the default account (and consequently the default data file) can help. Here is how to do this without opening Outlook:

  1. Go to Control Panel > Mail.
  2. In the Mail Setup window, select Data Files… . Change settings for the Outlook Data Files.
  3. In the Account Settings window, choose another account that has a valid data file and click Set as Default.
Change the default Outlook account.

Once the default account is changed, try starting Outlook again. If the original data file becomes available later, you can switch back at any time.

Fix 7. Repair Microsoft 365 or Office

If Outlook's program files are damaged or incomplete, repairing the installation usually resolves the issue. Here is a quick way to do this:

  1. Navigate to Settings > Apps > Installed apps.
  2. Find Microsoft Office or Microsoft 365 in the list.
  3. Click the 3-dots to the right of the app and select Modify.
  4. Pick Quick Repair first. Once the repair finishes, restart your computer and try opening Outlook again.
  5. If Outlook still won't open, try Online Repair.
Repair the Microsoft 365 installation.

For more details, see How to repair Outlook 365 – 2013.

Fix 8. Create a new Outlook profile

If neither repairing the data file nor fixing the Microsoft 365 installation helps, the problem may lie in your Outlook profile.

Opening Outlook with a new profile can help you determine whether the original one is corrupted. The steps are:

  1. Create a new profile. Go to Control Panel > Mail > Show Profiles > Add. Enter a name for the new profile and click OK.
  2. Add a single account. Follow the prompts to add your email account. If possible, start with an Exchange-based account as it syncs with the server and usually avoids issues related to local Outlook data files.
  3. Choose to be prompted for a profile. After the profile is created, enable Prompt for a profile to be used, then click OK. Prompt for an Outlook profile to be used.
  4. Test Outlook. Launch Outlook with the new profile. If it opens normally, you can begin adding your other accounts.
  5. Import data. If you have a POP3 account, you can try importing emails and other data from your old PST file.

Note. If the original PST file is severely damaged and repair attempts weren't successful, you may see this error message again: "Cannot start Microsoft Outlook. The set of folders cannot be opened." In that case, the only way is to use the new profile without bringing data from the corrupted data file.

For more information, see how to create a new Outlook profile.

How to fix startup issues with the new Outlook app

If you are using the new Outlook for Windows and it won't open, the underlying causes differ from the classic desktop version. The new app doesn't rely on local .pst or .ost files, so issues related to corrupted data files don't apply here.

To troubleshoot the new Outlook not opening:

These steps address the most common reasons when the new Outlook fails to start.

Additional tips

Below are a few more ideas can help you pinpoint what's preventing Outlook from opening:

  • Temporarily disable antivirus email scanning. Some security tools interfere with Outlook's startup, especially if they scan data files.
  • Check free disk space. Low storage can cause Outlook to pause or fail when loading accounts.
  • Disconnect external devices. Occasionally, issues with mapped network drives or external storage paths referenced by Outlook can block startup.
  • Look for error codes. If Outlook shows a specific error code, note it down, and then research for a targeted fix on the web.

These small checks often reveal overlooked problems and can save you time before moving on to more advanced troubleshooting.

Hopefully one of the solutions described in this article has helped you get your Outlook opening again. If you've found another fix that worked for you, feel free to share it in the comments. Your experience might help someone else facing the same problem. Thank you for reading!

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19 comments

  1. Phew! thank you, thank you, thank you (million times)!!!

    I was so frustrated with this challenge that I wanted to pull my hair! (Receding hairline or not... )

    Then, I followed the steps one-by-one... and guess what? A small tick did the magic!!! COMPATIBILITY !!! I unticked it and voila! Three weeks down the line...

    I'm over the moon. Thank you once again!

    Thanx Svetlana! Greetings from the southern tip of Africa

    1. Thank you for your feedback, Manny :) I'm happy to know the suggestion worked for you.

  2. i just lost my outlook 2007 *.pst file almost 3.5gb e-mail because of when i backup the outlook to format my pc and i cut the outlook folder from the directory and past it in c:\ drive and when i copy it to d:\ drive it says can't copy the file "error message" first the archive file is coped and when .pst file start coping it comes like Corruption error...and i chkdsk the computer harddisk...the chkdsk is verfiying the data for long time and when i came back home the power was off and i turn on and when i check the out look data the .pst file goes 0kb...what can i do??? please help????

    1. Hi Danny,
      I'm very sorry but I do not know any easy (and even not easy) way to restore the damaged .pst file in this situation. I can only suggest addressing some local IT professional or service that specializes in data recovery.

  3. loading add in menus xml: an xml parser error
    This error occured in msoffice 2013 i.e while starting any of office products this error came .need help.

    1. Hello Milind,

      Try to uninstall all Outlook add-ins you currently have. If this does not help, repair your Office programs, as described here.

  4. If you are using O365/Office 2013 and launching Outlook 2013 and you are getting "loading profile" and it wont go away... and Outlook 2013 starts in safe mode, it is because there is a conflict with the color depth. Change colors to Windows 7 basic (16 bit color) and Outlook will load fine. Turns out this is obscure error and I noticed it when doing remote support. Color switches to basic, Outlook launches perfect, disconnect remote session and Outlook hangs again. OEM video drivers are the cause. I know for sure this is on Lenovo and HP systems using the Intel & Nvidia drivers. OEM updates did not help.

    1. David,

      I have spent two days trying to troubleshoot my problem of "loading profile" and after attempting most of the solutions above and several more I finally ran across your post regarding color depth conflict. Initially I read your post and moved on but then came back and BOOM now outlook works perfectly. Yes, I have a Lenovo by the way. Thanks much for your insight!

    2. Hi David,

      I would never think the conflict with the color depth could cause Outlook hanging. Thank you very much for sharing!

  5. Thanks for a great post.

    Running Office 2013 on Windows 8

    I have tried everything but still getting issues.

    As I have multiple email addresses I had multiple PST files.

    Created a new profile and imported emails from first old PST.

    Then re-installed email address with new PST files.

    Copied imported emails to new email PST files.

    Tried to import second PST file and got a repeat of the same issue (Cannot open.....)

    Should I reinstall Outlook, or will this not help.
    Any suggestions?

    1. Hello David,
      If this is a recent problem, you may try to reinstall Outlook 3013 without recently released SP1. If this does not help, then try running SCANPST.EXE several times until it reports any errors and create new mail profile WITHOUT an email address. The latter method helped Trish in similar circumstances, please see comment 23 above for the details.

  6. So I have been using Outlook 2013 on my Windows 8.1 laptop for three months. I was initially about to import ALL my old files from my old computer. Had all my old emails under "archive.pst". Last week I set up a new email account for work (MS Exchange server), and it worked fine. This morning, while I was looking at some options, Outlook crashed. I couldn't restart it, and in the end, I had to delete all my accounts and recreate them. This time I did not create the MS Exchange account, only the two Gmail accounts. I was able to open Outlook. I then tried to open "archive.pst" and it kept giving me an error saying I couldn't open it. Figuring it was corrupt, I tried the pstscan.exe file, with no luck. Fortunately, the file is backed up by File History, so I restored the file prior to setting up the MS Exchange account last week. Still got the same error. I went back as far as Dec trying to restore the file, and no luck. At this point, I am convinced it's not the PST file, but something about MS Outlook 2013, but I have no idea what. I can go back to my computer and get the original archive file from Dec 11th that was used when I did the original import, but I get the feeling it won't matter.

    Any suggestions? I have about 8 years worth of emails I would like to have back.

    Trish :)

    1. Hi Trish,
      It's hard to say what may cause this issue and I'm hesitant to give any advice not to make things worse.
      I believe the best way to tackle this would be to hand in your computer to some local IT professional.
      You can also try reinstalling Outlook 2013 from scratch and then importing the backed up pst file. BTW, SP1 for Office 2013 was released at the end of February, did you install it?

  7. Hi I have the "microsoft office outlook has stooped working" Error.
    Im running windows 7 and office 2007.
    Outlook opens and then a few seconds later I get the above error!
    I have tried everything!
    1.I did a repair
    2.Did a reinstall
    3.Did the scan pst.
    4.If I start outlook in safe mode it does the same.
    5.Did the reset nave pane.
    6.Created a new profile with new pst.
    7.I have even loggin in as a different user on windows.

    If I am missing something please help!!

    1. Hi,

      In order to fix this problem "microsoft office outlook has stopped working" Error. Running in Windows 7 and Office 2007.

      Go to C:\Users\JoeBloggs\AppData\Local\Microsoft\Outlook

      Find the outlook.pst file (check the date before the problem started i.e. 19/01/15

      Right Click on outlook.pst properties and select 'Restore previous version"

      Select the restore point and click on RESTORE & OK

      Restart Outlook and watch the emails download.

      Let me know how you get on.

      Melissa

      1. worked a treat for me!! thank you soooo much -

    2. Hi Corne,

      Did you set the newly created Outlook profile as the default one? Also, have you tried to restore the profile?

      I'm asking just in case, to be 100% sure you've tried all the troubleshooting steps. If you have done this too and nothing worked, I can only suggest restoring your system to some point in the past when Outlook opened normally. Of course, Windows restore will delete all recent files and programs so you need to back-up everything prior to restoring.

      Also, you can contact Microsoft support, as David reported (please see comment 17) they did help him with this issue.

  8. I tried everything you mentioned, so thank you for all the great info!

    The clue for me was in the section "Create a new Outlook profile".

    My problem started when I was in process of deleting an email account I no longer used. During that time, Outlook crashed, which caused this error.

    1. Navigate to %localappdata%\Microsoft\Outlook.
    a. It is possible this could be located in %appdata%\Microsoft\Outlook.
    2. Find the .ost (Outlook Data File) file causing the problem.
    3. Delete that file and start Outlook.
    4. If you are unsure of the file that is causing the error, delete all .ost files, BUT KEEP THE FOLDERS! (very important).

    Hope this helps anyone else running into the same problem.

    Take care!
    Phil

    1. Finally a fix!!

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