When you connect Microsoft Outlook with Exchange Server, Microsoft 365, or IMAP account, your emails, contacts, and other mail items are stored in OST file. It is a local offline copy of your mailbox items. Sometimes, while accessing the file, the application shows an error – Outlook data file (OST) access denied. The complete error message may appear as:
Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. File access is denied. You do not have the permission required to access the file .ost.
From the error message, it seems that the user account doesn’t have the required permissions to access the OST file. However, there might be several other reasons that can cause such an issue. In this guide, we’ll explain the common causes of this error and provide some practical solutions to fix the issue and restore access to mailbox data.
Reasons for the Outlook OST File Access Denied Error
Outlook cannot access the OST file if your account doesn’t have the necessary permissions on the file or the folder where it is stored. But there are several other reasons that may also cause the access denied error, such as:
- Damaged or Corrupted OST File: If your OST is corrupted or damaged, then Outlook may fail to read the file and trigger this error.
- Storage Drive Issues: Disk errors, insufficient storage space, or problems with the drive containing the OST file may prevent Outlook from accessing it.
- Interference from other Applications: Applications, such as antivirus software, may interfere with the Outlook functionality, preventing it from accessing the OST file.
- OST File is Associated with Other Outlook Profile: Outlook cannot access the OST file if it is created in another profile.
- Faulty or Incompatible Add-ins: Third-party add-ins, if faulty or incompatible, may interfere with Outlook’s normal operation, causing the access denied issue.
- Corrupted Outlook Profile: Damaged or corrupted profile may prevent Outlook from accessing the associated data file.
Solutions to Resolve Outlook OST File Access Denied Error
To solve the ‘file access is denied’ error in Outlook 2010, 2013, 2016, or 2019 on Windows, you can follow these solutions.
Solution 1: Check File Permissions
Incorrect or lack of file permissions on the data file, i.e., OST, can prevent you from accessing your account as Outlook fails to access or read/write the file. Follow these steps to check and assign the required permissions:
- Open File Explorer and navigate to Outlook OST file location. If you don’t know the location, refer to our guide to locate the OST file.
- Right-click on the file and choose Properties.
- Click on the Security tab and click the Advanced button.
- Click Change and then click on the Enter the object name to select box (examples) box. Next, type your username and click the Check Names button.
- Select your username (or it will automatically fetch if there’s only 1 account matching your name) and then click OK.
- Under the Permissions tab, check ‘Full Control’ is mentioned under the ‘Access’ column beside your username. Click OK.
- Now restart MS Outlook.
If the error persists, head to the next solution.
Solution 2: Disable UAC or Run Outlook as Administrator
If the OST file is relocated or stored at a location that requires UAC (User Access Control) permission token, such as C:\Program Files\ or a similar location where you don’t have appropriate permission to perform this operation, it can also lead to the access denied error in Outlook.
However, this can be quickly resolved by running Outlook as administrator. For this, right-click on the Outlook application icon and then choose ‘Run as administrator.’
Alternatively, you may also disable the UAC. However, disabling UAC is not recommended as it compromises the system security.
Solution 3: Close Conflicting Applications
Applications such as Lync and Skype for Business also access and store information in OST data files. These applications may interfere with Outlook’s functionality, which may cause errors such as Outlook data file access is denied.
To resolve the error, you can close all the applications that may have access to your OST file. The steps are as follows:
- Right-click on the Taskbar and choose ‘Task Manager.’
- Click ‘More Details’ (skip if Task Manager is already displaying all the processes).
- Find and close the following processes:
- Communicator
- Lync
- Ucmapi
- Outlook
- Then open Outlook and check if the error is resolved.
If not, try closing the antivirus software (only for test purpose). If it is causing the error, you can add an exception for OST files in the antivirus software. If this doesn’t resolve the error, follow the next solution.
Solution 4: Disable Add-Ins
Incompatible or faulty add-ins could also lead to Outlook errors and issues. To fix this, you can find and disable incompatible or faulty add-ins. The steps are as follows:
- Close Outlook and press Windows + R.
- Type Outlook /safe and press Enter or click OK. This will open the Outlook in Safe Mode.
- Click File > Options and then click Add-ins.
- At the bottom, click on the Go button located beside Manage.
- Uncheck all the Add-Ins to disable them and click OK.
If you are able to access the Outlook account and OST file, enable each add-in (one at a time) to find the faulty add-in and then remove it.
Solution 5: Create New Profile
It’s possible that the profile you are using may have been damaged or corrupted. This can prevent Outlook from accessing the OST file, which results in a file access denied error. To resolve this, you can create a new Outlook profile. The steps are as follows:
- Open the Control Panel and then select Large Icons in ‘View by:.’
- Find and click on the Mail option.
- Click the Show Profiles tab and then click on Add to add a new profile.
- Enter your profile name and then press OK.
- Enter your name, login credentials, and other details, and then click Next
Restart Outlook and check whether the error is resolved. Make sure to set the newly created Outlook profile as the default profile.
Solution 6: Convert OST to PST
OST file is encrypted with MAPIEntryID GUID key and requires authentication from authorized MAPI profile. Thus, if you try to access or open an OST file from Outlook profile that isn’t associated with the OST file, you may receive the file access denied error.
In such a situation, you can download and install Stellar Converter for OST. The software helps you extract and save mail items from inaccessible or orphaned OST files to PST format, which you can import into your Outlook profile.
This OST to PST converter tool can also help you restore the mail items from such inaccessible OST files directly to your Outlook profile or export to live Exchange mailbox or Office 365 account.
If you have a small OST file of up to 500 MB, you can convert it to PST for free by using the Stellar Online OST Converter via a web browser. It doesn’t require installation of Outlook or any other additional software. The Premium edition of this online OST converter can also convert OST file of up to 5 GB.
Wrapping Up
It’s difficult to find the exact reason behind the Outlook OST file access denied error as it may occur due to several reasons. In this guide, we’ve explained some effective solutions to fix this Outlook error. However, you can use Stellar Converter for OST to regain access to your mail items. The software helps you by converting the inaccessible OST file to Outlook importable PST format. You can reset your Outlook account, configure a new profile, and then import the converted PST file to regain access to all your mail items.
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