There are several precautions we advise before you start importing an OST file into Outlook, Such as,
Backup: Take a backup of the original file before performing any actions on it. To ensure you have the file intact.
Use the copy of the OST file: Avoid directly modifying or tampering with the original OST file.
Check for Permissions: Make sure you have the necessary permissions to access the OST file.
Encryption keys: Ensure you have the correct encryption keys or password for encrypted or password-protected OST files.
Avoid Overwriting: Do not overwrite any existing data in the destination profile. Always choose the option to import the data into a new folder or merge it carefully, depending on your needs.
Can You Directly Import an OST File Into Outlook?
No. Outlook does not allow you to directly import an OST file using the built-in Import/Export wizard. OST (Offline Storage Table) files are encrypted and tied to the specific Exchange or Microsoft 365 account and Outlook profile that created them. Because of this binding, Outlook treats an OST from a different profile or a decommissioned server as unreadable. The short answer to “can you import an OST file into Outlook” is: not directly, but you can absolutely access all your data with the right two-step approach.
The standard workaround accepted by Microsoft is to first convert the OST file to a PST (Personal Storage Table) file, then import that PST into any Outlook profile using the Import/Export wizard. If the OST file is still connected to an active account, Outlook’s built-in export tool can perform this conversion. If the account is no longer accessible, for example, after an Exchange server decommission or an orphaned Outlook profile, a third-party OST to PST converter is required to unlock and extract the data.
Understanding this limitation upfront saves hours of troubleshooting. The table in the next section compares all available methods so you can choose the fastest path based on your specific situation.
Troubleshooting: Outlook Error 0x80040116 and OST Corruption
Outlook error 0x80040116 appears when Outlook tries to access an OST file that is either corrupted, locked by another process, or incompatible with the current profile. The full error typically reads: “The operation failed. An object could not be found.” It most commonly shows up after a forced shutdown, a failed Exchange sync, or when you try to open OST file in Outlook after moving it from another machine.
The first thing to try is running the built-in repair tool. Close Outlook completely, then navigate to C:\Program Files (x86)\Microsoft Office\root\Office16\ (the exact path varies by Office version) and run SCANPST.EXE. Browse to your OST file, click Start, and let the tool complete the scan. If it finds errors, click Repair. Run it two or three times back to back, a single pass does not always catch all corruption. After repair, reopen Outlook and check whether the error persists.
If Scanpst cannot repair the file, or if it reports that the file is too damaged to fix, the OST is effectively unreadable by Outlook natively. At that point, a third-party converter is the only option that can extract data from a partially corrupted file. Common signs that an OST file is corrupted before you even see an error code include: Outlook taking more than five minutes to load the mailbox, calendar items disappearing randomly, or the OST file size jumping to an abnormally large number (some corrupted files balloon past 50 GB). Do not ignore these symptoms, a corrupted OST left to grow will eventually hit a size limit and become completely unreadable.
Methods to Import OST into Outlook
Follow the step-by-step process to import an OST file into Outlook:
Method 1: Convert OST to PST File and Import into Outlook.
Step 1: Converting the OST to PST File
- Open Outlook, click on File and select Open & Export.
- Click on Import/Export.
- Click on Export to a File and click Next.
- Select Outlook Data File (*.pst) and click Next.
- Select the folders you want to convert, select the location to save the converted PST File, and click on Finish.
Step 2: Importing the converted PST File
Now import the PST file into Outlook profile using the Import/export wizard:
ALSO: If the OST File is inaccessible, consider using a third-party OST to PST converter tool to convert it into a PST File.
- Open Import/Export wizard
- Click on Import from another program or file and click Next.
- Choose Outlook Data File (.pst) and then click on Next.
- Browse for the PST file and choose replace duplicates with items imported and click on Next
- Select all the mail items and account, then click on Finish
Method 2: Outlook’s Archive Feature
- Open Outlook, click on the File, and click on Options.
- Select the Advanced option, then click on Auto Archive Settings.
- Set the auto archive settings as per your requirement. Set the day count to run auto archive and set a count to clear old mails.
- Once done, click OK, and Outlook will automatically create an OST email archive in PST form.
Now you can import the PST file into Microsoft 365 or Outlook using the Import/Export wizard (Follow the above-mentioned steps)
Method 3: Using Outlook Transfer Tool
If you have multiple OST files or large .ost files, there is a risk of data loss during the import process.
To simplify this, you can use an Outlook Transfer tool to complete the import and export outlook data files in just a few clicks for Office 365/Exchange Server accounts.
We recommend using Rikvr Transfer for Outlook to import OST files to Outlook 2021, 2019, 2016, 2013, 2010, and other versions of Outlook.
Backup the OST File:
- Close Outlook and related applications.
- Open Rikvr Transfer For Outlook and click on Transfer Outlook and then Backup.
- Select Advanced Backup and create a backup of the OST file.
Import the OST File:
- Select the Transfer option, select the recently generated backup file and click Next.
- Select the OST file and click Next
- Choose all the PST files or select your choice.
- Click on Finish to import the OST file into Outlook
How to Import OST File Into Outlook Office 365 and Outlook Online
Outlook Online (the browser-based version at outlook.office.com) has no native import tool for PST or OST files. You cannot upload an OST or PST directly through the web interface. To get OST data into a Microsoft 365 mailbox, you need to either use the desktop Outlook client to sync the imported PST up to the cloud, or use the Microsoft 365 admin center’s Network Upload feature for bulk migrations.
For individual accounts, the simplest route is to convert the OST to PST, then open the PST in Outlook desktop (any version connected to your Microsoft 365 account), and drag the folders from the PST into your primary mailbox. Outlook will sync those items to the cloud automatically. This works for mailboxes under 50 GB. For larger migrations or when you need to import OST file in Outlook Office 365 at a business scale, Microsoft provides the PST Import Service inside the Microsoft Purview compliance portal. You upload PST files to Azure Blob Storage and map them to specific mailboxes using a CSV mapping file. This requires a Microsoft 365 admin role and an active import job created in the compliance center.
One thing to be clear about: Outlook Online itself never touches the OST file. The OST exists only on the local machine where Outlook desktop is installed. The web client reads from the Exchange or Microsoft 365 mailbox directly. If you are trying to recover emails from an OST file belonging to a decommissioned Office 365 tenant, the PST import service above will not help either, the destination mailbox must be active. In that case, convert the OST to PST and store it locally as your archive.
How to Import OST File Into Outlook on Mac
Outlook for Mac does not support OST files at all. It uses the OLM format for local data, so you cannot attach an OST file to Outlook on Mac directly. The only supported path is to convert the OST to PST first, then import that PST into Outlook for Mac. The conversion has to happen on a Windows machine or via a Windows-compatible converter tool, because the OST format itself is a Windows-only Outlook construct.
Once you have the PST file, open Outlook for Mac, go to File > Import, and select Outlook for Windows Archive File (.pst). Choose the PST file you converted, and Outlook for Mac will pull in your mail, calendar entries, and contacts. Large PST files (above 5 GB) can take a significant amount of time, and Outlook for Mac may appear unresponsive during the import. It has not crashed, it is processing. Leave it running.
If you are trying to open an OST file in Outlook for Mac without converting it first, you will hit an unsupported file type error every time. There is no workaround for this within Outlook itself. The PST conversion step is not optional on Mac. On Apple Silicon Macs running Outlook 16.x, the import dialog path is identical, File > Import, so version differences do not affect the process here.
Which Method Should You Use? A Quick Comparison
Not every situation calls for the same solution. Use the comparison below to decide which approach to import your OST file into Outlook fits your specific scenario. Three main paths exist: the manual Export/Import wizard built into Outlook, the ScanPST (Inbox Repair Tool) route for corrupted files, and a dedicated third-party OST to PST converter tool.
| Method | Best For | Account Must Be Active? | Handles Corruption? | Cost |
|---|---|---|---|---|
| Manual Export (Import/Export Wizard) | Active Exchange or Microsoft 365 accounts | Yes | No | Free |
| Outlook Archive Feature | Routine backups and older email archiving | Yes | No | Free |
| ScanPST (Inbox Repair Tool) | Minor OST or PST file corruption | Yes (recommended) | Minor issues only | Free |
| Third-Party OST to PST Converter | Orphaned OST, decommissioned Exchange, severe corruption | No | Yes | Paid |
If your Exchange or Microsoft 365 account is still active and your OST is healthy, start with Method 1 (the manual Export wizard). It is free and built into every version of Outlook from 2010 through 2021. If the account no longer exists or Outlook throws an error when trying to open the OST file, skip directly to Method 3 and use a dedicated transfer tool. ScanPST is useful as a preliminary repair step before attempting any import, but it is not a conversion tool and will not produce a usable PST on its own.
When to Use Each Import Method
The right method depends on whether your OST file is still connected to an active Exchange or Microsoft 365 account, how large it is, and whether you have Outlook open at all. If your account is active and Outlook can still sync, exporting directly to PST via File > Open & Export > Import/Export is the fastest route. You get a clean PST with no third-party software required.
If the OST is orphaned, meaning the Exchange server has been decommissioned or the account no longer exists. Outlook will refuse to open it, and the manual export route is unavailable. That is the scenario where a dedicated OST to PST converter is not optional, it is the only path. The Archive method (Method 2) only works while the account is live, so do not attempt it on an orphaned OST file.
| Scenario | Recommended Method | Outlook Access Required? |
|---|---|---|
| Active Exchange or Microsoft 365 account | Method 1 (Export to PST) | Yes |
| Scheduled, recurring email archiving | Method 2 (Auto Archive) | Yes |
| Orphaned OST file or decommissioned server | Method 3 (Rikvr Transfer Tool) | No |
| Corrupted OST file | Method 3 (Third-party tool) after Scanpst repair | No |
| Multiple or large OST files (>10 GB) | Method 3 (Third-party tool) | No |
| Importing into Outlook on Mac | Convert to PST first, then use Outlook for Mac import | Yes (Mac) |
Conclusion
We hope this article helped you import the OST file into Outlook. Ensure you choose the method that works best for you and follow the necessary precautions before starting the import process. If you’re dealing with critical emails or important information, be sure to back up the PST file and store it in a secure location.
Frequently Asked Questions
As OST files are tied to the specific account that created them and are meant for offline access, they cannot be directly imported into Outlook.
Simply add an Exchange, IMAP, or Office 365 account, and Outlook will automatically create an OST file for offline access. The OST file is linked to your account and synced with the mail server.
Outlook might not load an OST file if the OST is corrupted, or a mismatch between the OST file and the associated account, or problems with the Outlook profile.
Outlook cannot open an OST file for several specific reasons. The most common is that the OST file has become orphaned, the Exchange or Microsoft 365 account it was created with no longer exists or is no longer accessible from the current machine. Outlook enforces a strict binding between the OST file and its originating account credentials, so even a slightly different profile setup will block access.
A second frequent cause is file corruption. If Outlook crashed during a sync, the hard drive encountered bad sectors, or the OST file was forcibly moved or renamed, the internal structure can become damaged. In these cases, Outlook may display error code 0x80040116 or simply fail to load the file. Running Microsoft’s built-in ScanPST tool (found at C:\Program Files\Microsoft Office\root\OfficeXX\SCANPST.EXE) can repair minor corruption, but severe cases require a third-party OST repair and conversion tool. Additionally, an OST file that exceeds Outlook’s size limit or resides on a network drive with restricted permissions may also fail to open, always ensure the file is stored locally and that your Windows user account has full read/write access to the file before troubleshooting further.
Converting an OST file to PST is the essential first step before you can import OST data into any Outlook profile. If your Exchange or Microsoft 365 account is still active, open Outlook, go to File > Open & Export > Import/Export, select Export to a File, choose Outlook Data File (.pst), select the folders you want to export, and click Finish. Outlook will generate a fully portable PST file saved to the location you specified.
If the account is no longer active, for instance, after an Exchange decommission or a deleted Microsoft 365 user, the built-in wizard will not work because Outlook cannot authenticate against the original server. In this scenario, use a dedicated third-party OST to PST converter, which reads the OST file’s internal structure directly without requiring server authentication. Once the PST is generated, open Outlook, go to File > Open & Export > Import/Export, select Import from another program or file, choose Outlook Data File (.pst), and follow the wizard to merge the data into your active mailbox. This two-step process works across Outlook 2010, 2013, 2016, 2019, 2021, and Microsoft 365 on both Windows and Mac.
