
The answer is no, you cannot import an OST file ‘as is’ in Office 365. However, there’s a way out, you can convert the OST file to PST file — extract the mailbox data from OST in PST— which can be readily imported in Outlook, be it an on-premises setup or Office 365.
In this blog post, we’ll share the methods to import OST file in Office 365 via conversion into PST or through Stellar Converter for OST you can directly export to office 365.
Methods to import OST file into Outlook or Office 365
Default Method: OST to PST export via Outlook.
This is based on exporting the OST to PST file via Outlook, and then further using Network Upload Office 365.
Note: This method is only applicable to OSTs that have the associated mailbox available on Exchange. Otherwise, use method 2 for converting OST file into PST.
- The OST to PST Converter software
This is largely automated, with a single procedure to convert OST to PST and import PST in Office 365 or you can also directly export OST to Office 365.
Default Method
To use the default method, first export the OST file into PST format.
The default method comprises two processes – exporting OST to PST and importing PST to Office 365:
- Export OST to PST
- Import the PST file to Office 365
Export OST to PST format:
Open Microsoft Outlook & export OST to PST
1. Open Outlook and follow these steps: click on the File >> Import/Export>>Export to a file >> Next
2. Select Personal File Folder (PST) option and go to Next button.
Note: You can also choose a specific folder or sub-folder to export to PST file.
3. Click Browse to save the converted file location and click Finish to export the OST file to PST format.
Note: This option is not valid only when the OST file is in an orphaned state.
Import PST to Office 365
Network Upload method:
Network upload method is used to bulk-import PST files into office 365. All the PST files are uploaded at a centralized location like file server or shared drive and uploaded to Office 365 with the help of Azure AzCopy tool. The Administrator trying to import the PST file must be assigned Mailbox Import Export role. Also, ensure that the administrator is a part of the Global Administrator in Office 365.

This method consists of six processes and each process is further broken down into multiple steps.
- Copy the SAS URL and install Azure AzCopy
In this process, you have to download and install the Azure AzCopy tool to upload PST files to Office 365. Ensure that the downloaded copy is of the right version and copy the SAS URL for your organization. Since the URL is unique to any organization, it has to be protected.
This process also involves signing-in with an administrator account in the Office 365 environment on https://protection.office.com and selecting the option of uploading data or shipping hard drive to a physical location.
- Upload your PST files to Office 365
This process includes the steps to upload and store data in Azure storage location, located in regional Microsoft datacenter from where your Office 365 account is managed.
- View a list of the PST files uploaded to Office 365
An optional process that verifies PST files from the shared folder or file server are successfully uploaded to the Azure Blob.
- Create the PST Import mapping file
This process creates a CSV file to specify which user mailboxes will the PST file will be imported to. Allows to download a copy of PST Import mapping file and open or save it on local computer. Through this step, you can edit the PST data available in the Excel file.
- Create a PST Import job in Office 365
Office 365 analyzes the data in the PST files and provides an opportunity to filter the data which is imported to the specified mailboxes. The PST-import task can be performed through https://protection.office.com/ link.
- Filters data and starts the PST Import job
Office 365 analyzes PST data to import the data in the PST file. Once the data is analyzed, it can be imported directly. You can apply filters to import only specific data.
For further queries and detailed steps, refer the content available on this link.
Limitations: In this method, all the permissions take 24 hours to set up prior to use, and if the import fails then you have to delete the email account and start again, this takes a substantial amount of time. So what is the best method?
OST to PST Converter software
Stellar Converter for OST – Technician is the best method to export OST file to Office 365. Steps to import an OST file into Office 365 with the help of an OST to PST converter software:
Note: This method imports OST file to Office 365.
1. Launch and open Stellar Converter for OST Technician
2. Browse or find OST file to be imported
3. Select the OST file for conversion
4. Click Convert. The software scans and displays the file items
5. To import in Office 365, Click on Save Converted Save File in the menu bar and select Export to Office 365 from Save Option Dial box.
6. Provide valid credentials and the software imports the OST file into directly Office 365. Click Ok to conclude the process
Conclusion
In this post, we shared two methods for importing OST file to Office 365, the software-based approach can facilitate importing of any kind of OST file in Office 365, as the software imports both orphaned and working OST files.
In the other approach — OST to PST file export via Outlook —the user has to first export an OST file into PST file and then import the PST file in Office 365 by using lengthy and time taking processes. This method doesn’t work when the OST file is in an orphaned state. If you have time and energy to perform the steps and your OST file is in a working state, then it is a good-to-go method.