Error Solved: “The file username.ost is in use and cannot be accessed” in Outlook
Summary: OST is an Outlook data file and problems with OST file often results in errors such as ‘The file xxx.ost is in use and cannot be accessed’. This can be resolved by converting the faulty OST file to PST format with Stellar Converter for OST. However, there are a few troubleshooting methods that you may apply to fix the Outlook error.
In Microsoft Exchange, if Cached Exchange Mode is ON, a replica of mailboxes residing on the server is created on the local machine with .ost extension. This ‘cached mode’ allows users to work offline on Outlook and improves Outlook performance.
When the server comes back online, all changes made in the local mailbox cache (.OST) are synchronized with the mailbox on the server. However, sometimes due to a problem with OST file, an Outlook user may experience errors such as
‘The file C:\users\….username.ost is in use and cannot be accessed. Close any application that is using this file, and then try again. You might need to restart the computer.’
Reasons Behind the Error
The error may occur due to several issues but often appears when a user tries to “Share” or “Save and Send” MS Office file via applications such as MS Word, PowerPoint, Excel etc.
The error indicates that the Outlook OST file is being used by another program and closing it may resolve the error. However, spotting the particular program or process that is causing the error can be difficult for most users. The error also suggests user to restart the system which usually resolves the error.
But it isn’t necessary that the OST file is being used by another program. There could be several other reasons which may lead to the error, such as:
- Synchronization issue between the OST and associated Exchange mailbox
- Conflicting applications with Microsoft Outlook
- Multiple users trying to access the same OST file (typically in case of networked systems)
- Unreliable network connectivity or slow internet connection
- Unauthorized access to OST file
- Processes like Office Communicator 2005/2007, LYNC, UCMAPI.EXE etc. running in the background
How to Resolve the Error in MS Outlook 2019, 2016, 2013, 2010 & 2007?
Following are a few methods that can help you troubleshoot and fix “The file xxx.OST is in use and cannot be accessed” error:
Method 1: Quit MS Outlook and Related Processes
Make sure that multiple instances of Outlook aren’t running on the same machine and no other related process is running that needs access to the OST file. This can cause the OST file to be marked as “in use”. Here are the steps:
- Close Outlook and open Task Manager
- Select the “Processes” tab
- In the list, look for “Outlook”, “LYNC”, “Communicator”, or “UCMAPI” named processes
- Click on such processes and hit “End Task” button one-by-one
Then check if the error is resolved.
Method 2: Disable Exchange Cached Mode
Another way to fix the ‘OST can’t be accessed’ issue is to turn OFF the “Cached Mode”. Follow these steps,
- Quit Outlook and then open Control Panel
- Go to Mail> Email Accounts> Email
- Select your email-id and then click on the “Change” button
- Uncheck “Use Cached Exchange Mode…”
- Click on the Next button
- Click on Finish
Don’t forget to turn Cached Mode ON even if the error isn’t fixed.
Method 3: Find and Disable Problematic Outlook Add-ins
Though add-ins are meant to enhance Outlook’s functionality, faulty add-ins can sometimes cause trouble such as making OST files inaccessible.
Thus, disabling the problematic add-ins may fix this error and you may access the Outlook account and OST file. To find if the error is a result of a faulty add-in, you need to start Outlook in Safe Mode. Follow these steps,
- Close Outlook and then press Windows+R
- Type Outlook /safe and press ‘Enter’
- Use Outlook normally and check if the error is fixed
If fixed, run Outlook in normal mode and disable add-ins, one at a time and observe Outlook for the error. This will help you uninstall the faulty add-in and keep non-faulty add-ins.
Method 4: Repair OST file with Inbox Repair Tool
If the error is caused by some problem with the OST file such as read/write permission or integrity issue, you can use Microsoft’s inbuilt Outlook data file inbox repair tool called ScanPST.exe.
Earlier, Microsoft used to provide ScanOST.exe to fix OST problems. But ScanOST is discontinued from Outlook 2010.
By repairing the Outlook OST file with ScanPST.exe, you may get rid of the error – “The file xxxx.ost is in use and cannot be accessed”. Here are the steps to use this utility,
- Close Outlook and launch the ScanPST.exe tool. To find ScanPST.exe, browse these locations based on Outlook version installed on your system,
- exe location for Outlook 2019/Office 365
- C:\Program Files\Microsoft Office\root\office16\
- exe location for Outlook 2016
- 32-bit Outlook: C:\Program Files (x86)\Microsoft Office\Office16\
- 64-bit Outlook: C:\Program Files\Microsoft Office\Office16\
- exe location for Outlook 2013
- 32-bit Outlook: C:\Program Files (x86)\Microsoft Office\Office15\
- 64-bit Outlook: C:\Program Files\Microsoft Office\Office15\
- exe location for Outlook 2010
- 32-bit Outlook: C:\Program Files (x86)\Microsoft office\Office 14\
- 64-bit Outlook: C:\Program Files\Microsoft office\Office 14\
- Click ‘Browse’ and navigate to the directory on your system where Outlook OST is stored. The default location is C:\Users\%username%\AppData\Local\Microsoft\Outlook
- exe location for Outlook 2019/Office 365
- Click ‘Start’. After the scan, if the tool finds errors, click ‘Repair’
After repair, start Outlook and check if the error is fixed.
NOTE: ScanPST.exe does not work for orphaned and encrypted OST files and file sizes above 2 GB.
Method 5: Recreate OST File
If the OST file is still inaccessible and the error isn’t resolved, you can try to recreate the OST file. This can help in rectifying minor corruption issues within the OST file.
To do so,
- Close Outlook and go to the OST file location
- Then rename the OST file extension with .bak extension
For instance, if the OST file name is abc@xyz.com.ost, rename it to abc@xyz.com.ost.bak
- Then open Outlook. This will re-create the OST file and sync the mailbox items
In case this also doesn’t work, then there’s no other option but to convert the OST file data to PST. PST is also an Outlook data file that can be imported into any Outlook profile. The process is explained in the next method.
Method 6: Convert OST to PST
To convert OST to PST, there are two ways,
- Manually via Outlook Import/Export wizard
- By using OST to PST Converter Tool
Export OST to PST via Outlook Import Export Wizard
If you can access Outlook, you may try these steps to export OST to PST file via Outlook Import/Export wizard.
- Launch Outlook and go to File> Open> Import
- This will open the ‘Import and Export Wizard’
- Select ‘Export to a file’ and click on the ‘Next’ button
- From the next screen select ‘Outlook data file (.pst)’ and click on ‘Next’
- Click on ‘Browse’ to pick a destination to save converted file and click on ‘Finish’
Note: Since the OST file is inaccessible, the Outlook Import/Export wizard may not work. In such cases, use the OST to PST converter tool.
Convert OST to PST by using Stellar Converter for OST
Stellar Converter for OST makes the process of converting the inaccessible OST to PST quite easy. With its intuitive graphical user interface and useful features, an Outlook user can easily export the mailbox in OST file to PST, even if the file is orphaned or encrypted. It converts OST to PST with 100% data integrity and precision.
This tool can help you prevent “The file username.ost is in use and cannot be accessed” error and other errors associated with OST files. You can download the demo version to scan and preview all your mailbox components in OST file for free before saving it to .pst file.
Further, you may choose to export OST mailbox items to other file formats. There’s a Technician version also that can export your OST mailbox to Live Exchange server, Office 365 account or Outlook profile directly.
Wrapping Things Up
The guide helps you resolve “The file username.ost is in use and cannot be accessed” and makes OST file accessible through various troubleshooting methods. However, the best and most reliable way to fix the error and avoid further damage to the OST file, use OST to PST converter tool such as Stellar Converter for OST.
But you may try the troubleshooting methods at your discretion. If they fail, don’t hesitate to use this trustworthy product.
Read: What MVP’s says about Stellar Converter for ost.
Hello i have Outlook 2019, if i want to open outlook this writes me that there is a problme with my .ost file.
But if i launch reapirost.exe this can nit find the .ost file -) i tried to find but i have no .ost or .pst file in my computer. Somebody advices me to erase .ost and .pst files and after launching outlook it creates new files – but i can not launch outlook because od problem with .ost? i also tried to reinstall office but the error is still the same. Thank you for any help i am exhausted
First, you should copy and backup the OST file from default location. But now if you have already deleted/erased it, you can try removing your current Outlook profile, which seems corrupted, and then add/create a new profile with your email ID.
I can’t more with manual tips. So, I am going to use Stellar Converter for OST.
Started to work on this problem in the early morning and just fixed! Credit goes to your perfect tutorial.
Our organization employees edit & saved the word file and facing .ost in use and cannot be accessed error. We have run scanost.exe application but can’t fix this error. Kindly suggest any other method.
You can run Outlook in compatibility mode. Follow below steps:
1. Go to your system desktop
2. Hold Control Key (Ctrl)
3. Double click on Outlook icon
4. Now, confirm the dialogue box that asks to fix OST file.
When I launched Outlook, I got the following error message:
“OST file is in use and cannot be accessed”
Then I tried to fix the error suddenly one more error occurs:
“Sorry, we’re having trouble starting Outlook. Only one version of Outlook can run at a time. Check to see if another version of Outlook is running, or try restarting your computer.”
Please suggest best solution.
To fix these errors, Restart your computer and run MS office repair program through Program & apps.
running an office repair via control panel, Programs & Apps resolved this issue for the ost profile in use error, you just select the program for office and hit change, then run a quick repair, if this doesn’t work a colleague suggested running gpupdate /force, and rebooting and if that doesn’t solve it then add a new profile for Outlook, but the office repair did the trick, hope this helps! 🙂
@Mary, Thanks for the tip!
Today when I tried to access Microsoft Outlook 2016, it suddenly crash and faced this error:
The file C:\Users\roger\AppData\Local\Microsoft\roger\outlook.ost is in use and cannot be accessed. Close any application that is using this file, and then try again. You might need to restart your computer.
How to resolve this error?
Kill all MS Outlook related processes through Task Manager and restart the computer. This is the simplest way to resolve this error.
I have tried it all the still Outlook is giving this error.
Will I be able to solve this issue, If I use Stellar Converter for OST?
Hi Oliver,
Just download the software for 100% free evaluation. Then, you would be able to make a right decision.
Thank you so much. I tried many complicated ways from many sites. This was so simple. Worked for me.
You can also use this licence key for the lifetime.