Fix: Unable to access Outlook username.ost file. (Solved) – wintips.org

If you can’t open Outlook because the username.ost file is in use or corrupted, then continue reading below to resolve the issue.

If you have enabled the “Use cached exchange mode” option in your Outlook account settings, Outlook downloads and stores all your e-mail messages on the Exchange server locally in a file named “username.ost”. * When Outlook is configured this way, users can see all their e-mail messages even when they are offline, and when they come back online, all their e-mail messages will be synchronized with the Exchange server again.

*Note: Here “username” is your Exchange account name. (eg john@office365.com.ost.)

If Outlook crashes while synchronizing Outlook with Exchange Server, due to a bad network connection or a sudden shutdown of the computer (for example, after a power outage), the following error message may appear when you start Outlook:

The file C:\Users\*****\AppData\Local\Microsoft\Outlook\username.ost is in use and cannot be accessed. Close any application that uses this file and try again. You may need to restart your computer.

As a result of this error, Outlook won’t start and users can’t access their email because the OST file is in use or corrupted.

HOW TO FIX: An Outlook .OST file is in use and cannot be accessed in Outlook 2019, 2016, or Outlook for Office 365. *

* Offer: Before trying any of the methods below, the first thing you should do is save all your current work, then close all running programs and restart your computer. These simple steps will often fix the “Outlook username.ost file is in use and cannot be accessed” error.

  1. Close all Outlook related processes.
  2. Disable Exchange cached mode.
  3. Recover Outlook OST file.
  4. Repair Microsoft Office.
  5. Force Outlook to recreate the Outlook OST file.

Method 1: Kill all Outlook related processes.

Certain processes and services running in the background can cause Outlook to fail to open with the “Outlook username.ost file is in use and cannot be accessed” error. So, proceed as follows:

1. press CTRL + SHIFT + ESC to open Task manager.

2. In Procedures tab, right click in the following processes (if running) and select Finish the task.

  • Microsoft Outlook
  • Microsoft Lync
  • Skype
  • WebEx

FIX Outlook username.ost is in use and cannot be accessed

3. Once done, restart Outlook and see if the issue is resolved. If Outlook still won’t open because the “username.ost” file isn’t accessible, go to the next method.

Method 2: Disable and re-enable cached exchange mode.

The next way to fix the “username.ost is in use and cannot be accessed” Outlook error is to disable cached exchange mode and Outlook account settings.

1. Close the Outlook desktop application.

2. It’s open Control Panel, installation view by for small icon, then open it Mail (Microsoft Outlook).

control panel-mail

3. A Mail setup click the window Email accounts…

Configure Outlook mail

4. Above Email select the tab Account exchangethen press Change.

Outlook email accounts

5. uncheck the box with Use cached exchange mode, then press The next one and Termination. *

*Note: If “Use cached exchange mode” is grayed out, go to the next method.

Outlook cached exchange mode

6. Now launch Outlook and check if the error persists. Otherwise, close Outlook again and re-enable Exchange cache mode by following the steps above. If the error still occurs, continue with the next method below.

Method 3. Repair Outlook OST data file.

If Outlook opens the OST file, go ahead and fix it using it scanpst.exe utility (aka “Inbox Repair Tool”). For this:

1. comply with Steps 1-3 above to open Email account options.

2. Yes Information in the files tab, select the affected OST file and click on it Open the file location to find the storage location of the affected OST file on the disk.

correction forecast is not accessible.

3. Now open another Explorer window and navigate to the following location on your drive, depending on your version of Office:

Click to launch Office 365, Office 2019, and Outlook 2016:

  • C:\Program Files\Microsoft Office\root\office16\

Outlook 2019, 2016 (32-bit) and Windows (32-bit):

  • C:\Program Files\Microsoft Office\root\Office16\

Outlook 2019, 2016 (32-bit) and Windows (64-bit):

  • C:\Program Files (x86)\Microsoft Office\root\Office16\

Outlook 2019, 2016 (64-bit) and Windows (64-bit):

C:\Program Files\Microsoft Office\root\Office16\

Outlook 2013 (32-bit) and Windows (32-bit):

  • C:\Program Files\Microsoft Office\Office15

Outlook 2013 (32-bit) and Windows (64-bit):

  • C:\Program Files (x86)\Microsoft Office\Office15

Outlook 2013 (64-bit) and Windows (64-bit):

  • C:\Program Files\Microsoft Office\Office15

Outlook 2010 (32-bit) and Windows (32-bit):

  • C:\Program Files\Microsoft Office\Office14

Outlook 2010 (32-bit) and Windows (64-bit):

  • C:\Program Files (x86)\Microsoft Office\Office14

Outlook 2010 (64-bit) and Windows (64-bit):

  • C:\Program Files\Microsoft Office\Office14

Outlook 2007 and Windows (32-bit):

C:\Program Files\Microsoft Office\Office12

Outlook 2007 and Windows (64-bit):

  • C:\Program Files (x86)\Microsoft Office\Office12

4. Double click at SCANPST.EXE

Outlook pst data file repair

5. press Review and select the OST file from the location you see above.

scanpst.exe repair Outlook PST file

6. Finally, click on Start Click the button to start the repair process.

Outlook ost file repair

7. Now wait for the repair process to complete. (During the final repair step, you will be asked if you want to create a backup. Click Yes.)
8. When the repair process is complete, close the Inbox Repair Tool.
9. Start Outlook.

Method 4. Repair Microsoft Office.

1. press at the same time Windows image + R buttons to open the run command window.
2. Enter the following in the Run command window: appwiz.cpl and press Enter.

Open Programs and Features - Windows

3. In Programs and featuresselect Office Click and click on the version you have installed Change.

Repair Office 2016 - Office 2019

4. leave the Quick repair select an option and click on it Repair.

Quick fix Office 2016 - Office 2019

5. After the Office repair process is complete, launch Outlook and see if the error persists.

Method 5. Force Outlook to recreate the Outlook OST file.

1. Close Outlook.

2. using Steps 1-2 find the name of the OST file above and navigate to the location of the OST file on the disk.

3. Right click Pick and choose in the OST file Change the name.

4. Add an extension .OLD at the end of the filename to rename the OST file for backup reasons (eg from “john@office365.com.ost” to john@office365.com.ost .old). *

*Note: If you don’t have enough free space, you can delete the OST file or move it to another storage device.

5. Now open Outlook and allow Outlook to create a new empty OST data file and re-sync your emails. Once that’s done, delete the old OST file from your drive and you’re done.

That’s it! Which method worked for you?
Let me know if this guide helped you by leaving a comment about your experience. Please like and share this guide to help others.

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