Outlook crashing, hanging and freezing – common causes and solutions

This article describes some of the most common reasons that cause Outlook to become unstable, crash, hang or freeze.

If you are experiencing issues with your Outlook, try these items one-by-one and hopefully one of them will help.

Corrupted PST file

By far the most common reason for Outlook crashes, instability and unexplained weird behavior is a corrupted PST or OST file.

If you have an Exchange (or Office 365) account, you have an OST file. Follow the next section – “Corrupted OST file”. For other account types, follow this section.

Microsoft is aware of this issue and provides a tool to fix it – Inbox Repair tool (scanpst). Follow the steps listed in that Microsoft Knowledge Base article to run ScanPST. Run it on all your PST files.

Important: In many cases, ScanPST requires more than one pass to fix a corruption. Run ScanPST repeatedly, until it reports that there are no more errors.

In some cases, a corruption might be so bad that ScanPST is unable to fix it. ScanPST will tell you that there are no more errors, but you would still experience issues. In this case, you should create a new PST file and copy all items from the old PST into the new one. After you do that, close the old PST file (Right-click the top-most folder of the PST, then select “Close”) and start using the new one.

Note: You can also use scanPST to check and fix your OST files.

Corrupted OST file

To fix an OST file for an Exchange-based account, you simply rename it and let Outlook rebuild it from the server.

Before deleting the OST, check that Outlook is fully synced. (It should say “All folders up to date” in the status bar at the bottom of the main Outlook window).

First, find your OST file:

  • Click “File” in the upper-left corner of the main Outlook window.
  • Click the square “Account Settings” button, then the “Account Settings” menu command.
  • Switch to the “Data files” tab.
  • Select the OST file.
  • Click “Open File Location”. This will open File Explore and select the OST file.

Then rename the OST file, so Outlook rebuilds it.

  • Close Outlook.
  • Rename the OST file. For example “Mary.ost” to “DELETEME_Mary.ost”. (You can delete the old file later).
  • Restart Outlook and let it rebuild the OST file. Note: This operation might take a long time if you have a large Exchange mailbox, but you can still use Outlook while it happens.

For a non-Exchange account OST, such as IMAP, use the ScanPST method in the first section of this article.

Corrupted Profile

Sometimes an Outlook profile might get corrupted. In this case, you have to create a new profile.

Corrupted Outlook Configuration Files

[This section is no longer relevant. It applied to old versions of Outlook.]

In addition to PST, OST and profiles, Outlook has several other files which might get corrupted. If the above steps did not help, please try renaming outcmd.dat, extend.dat and Frmcache.dat as described in Part 2 of this article.

Misbehaving Add-ins

Running unnecessary add-ins may make Outlook slower and even cause stability issues. Check what add-ins you have installed. You probably have more add-ins installed than you think. Use the following instructions to see what add-ins you have installed and disable the ones you are not using. Leave only the Add-ins you absolutely must have in Outlook.

How to disable addins in Outlook 2016, 2013 and 2010
How to disable addins in Outlook 2007
How to disable addins in Outlook 2003

Keep Windows Up To Date

Regularly use Windows Update to keep your computer up to date with the latest patches and service packs. We recommend that you configure Windows to check for updates automatically.

Hope you found this article useful. If you have additional tips, please share them in comments below.

TechHit products will help you spend less time managing email and keep Outlook running in tip-top shape.

15 Replies to “Outlook crashing, hanging and freezing – common causes and solutions”

  1. I have this error in Outlook 2003. Can’t send and receive email.
    AppName: outlook.exe AppVer: 11.0.8010.0 AppStamp:43d16d53
    ModName: ntdll.dll ModVer: 5.1.2600.2180 ModStamp:411096b4
    fDebug: 0 Offset: 0000eddc

    1. JF,

      First, use Windows Update to ensure that your Windows and Office is up to date with the latest patches and service packs.

      After that, carefully follow all steps in the article above. Usually one of them will fix an issue like the one you are experiencing.

  2. A virus had invaded my computer and we had to reformat the disk. After that I found Outlook would on and off not load. It would hang at the loading profile stage. When a repair was done it would work two or three times and then hang again. I removed all add-ins except Norton and the problem seeemed to be fixed. However, when I wanted to send an email from files in Paperport (a PDF program) Outlook would not respond. I then also had problems sending emails from Adobe Acrobat. This morning, Outlook hung again. I did a repair and it opened OK. I suspect that Paperport is causing the problem. If I do not send the file from the thumbnail in Paperport but open it up first, I never get a hang up. Going back in my memeory, I think, but I am am not sure, that the originl problems in Outlook began after such an episode with Paperport. Prior to the Virus incident, everything always worked perfectly.
    What do you suggest?

    1. Paul, sounds like you have good reasons to suspect that Paperport might be related to this issue. If Paper port has an Outlook add-in, try disabling it to see if it makes a difference (you will find instructions in the article above).

      If that does not help, you might want to contact Paperport vendor for assistance.

  3. I can’t even get Outlook to upload. When I try I get this message: “The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action”. When I try to connect, it asks for my “Microsoft Exchange Server”, and I have no idea what that is. Can anybody help me?

  4. I have 64 bit Office installed and working fine until I also installed MS Visio 2007, a 32 bit application. This caused constant Outlook 2013 crashes. Seems you should not have 32 and 64 bit Office installations on your machine. I uninstalled Visio and all is well again, No more crashes.

  5. Thanks for sharing the article. It helped me a lot. Outlook is not extremely efficient with PST file space. When something is erased, it is left for a long time before it is actually erased from PST file. To fix this, select every PST file (for the most part called Outlook or Personal Folders), right click on it and choose Data File Properties >> Advanced >>Compact Now. This really erases all deleted messages, so Outlook will work faster and your PC have all the more free space.

  6. I just wanted to comment becuase i’ve found millions of threads, but no solutions. some people have the issue where Outlook continuously freezes and have not found a resolution even following all of the suggestions they still have problems. I’ve found an additional solution and wanted to share.

    1) navigate to the native exe file for outlook. 
    > should be something like: C:\Program Files (x86)\Microsoft Office\root\Office16
    2) Right click on the exe file (outlook.exe)
    3) click on “troubleshoot compatibility”> Click on “Trouble shoot program” (not “Try Recommended settings”)
    > check the box “The program worked in earlier versions of Windows but won’t install or run now”
    > select “Windows XP (service Pack 3)
    > Click “Test the program” This will launch Outlook in compatibility mode as Windows XP SP3.

    It seems to be the only way to activate compatibility mode for office programs. I tested this in Windows 10 in the following versions: 1703, 1709, & 1803 with success (the error became present after updating from 1607 to 1703), and outlook 2016 seemed to work just fine in 1607 and older.

    I’ve tested this with Office 2013/2016/o365. 2010 did not have the issue, 2007 did not have the issue, however i’m sure the troubleshooting would work for these versions for anyone else as well

  7. Hi,
    The issue notice with IBM Notes IMSMO, the syncing issue.

    All MS-Office 2010 has been noticed. What might be gone wrong?

    Please advise on this case.

    Salman Ahmed

  8. Hi, My Outlook had problems so I reinstalled it/ Microsoft but now it says this Microsoft product (Outlook) is inactivated. However in Control Panel it says the Microsoft in activated?

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