How to Import OST File to Office 365 Account? Best Solution

Written By Lovely Baghel
Published on: August 21st, 2025

Outlook mailboxes contain data for Cache Exchange mailboxes in the OST file format. Yet, sometimes users need this mailbox data in their on-premise Office 365 mailboxes for cloud storage and more security. At such times, one common query from the user is, “How can I import OST file to Office 365 for large batches from archived mailboxes in no time and with zero loss?” To answer this, we have curated this blog with traditional solutions and an OST to PST Converter.

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But before we proceed directly towards the steps, let’s understand how this import benefits different users.

Why Import OST to Office 365 is a Smart Choice?

The following table depicts a clear picture of why and how this import is crucial to ensure long-term data access.

Users	Impact of Import
IT Administrators	Centrally manage mailboxes, apply retention policies, and mandate regulations without Outlook.
End Individuals or Employees	Access Outlook data anytime, anywhere, on the web, mobile, or other devices with no restrictions.
Decision Makers	Risk of data loss for OSTs prone to corruption, encryption, or sudden deletion with long-term secure storage.
Legal Teams	Access to eDiscovery and audit logs, so that it’s easy to investigate during a dispute, audit, or compliance.

Thus, this isn’t just a technical import but a way to increase productivity, accessibility, and compliance of Outlook data across platforms.

Which Methods to Use to Import OST File to Office 365?

It is very simple to add OST to any Office 365 account because all you need is to convert the file into PST format. It is because Office 365 supports the PST file format, and you can directly access it without difficulties. Here, we will see a manual method for this task and a professional tool thereafter for swift and direct import.

Native Import OST into Office 365 for Free

The process is a bit lengthy and requires you to go through three stages for completion of the import. All the stages are explained in detail below:

Stage 1: OST to PST Conversion

You need to first go to File and then click on the Open & Export.
Further, from there, access the Import/Export wizard.
Choose for the Export to a File option afterwards, and click Next.
Later, select the PST format, click Next, and pick the OST files from the tree.
After that, click Next, choose the destination, and click Finish.

Stage 2: Import OST File to Office 365

To proceed with the steps here, first you need to fulfil these prerequisites:

AzCopy installed, Microsoft 365 admin access, and a CSV for mapping.

Furthermore, the steps are as follows:

Login Office 365 >> proceed to EAC (Exchange Admin Center).
Then, press Permissions and start the Organization Management.
A dialog shows up, click on “+” icon to add the MailboxImportExport role.
Further, press Add >> OK >> Save to complete the role setup.
After that, go to the Admin Center >> click Setup >> and then, Data Migration.
Press Upload File >> New Import Job >> enter the name and tap Next.
Then, choose Upload your Data >> Next >> and a window shows up.
Click on Show Network Upload SAS URL and copy the URL displayed.
Afterward, you must download the Azure AzCopy Tool and run it.
Permit folder and files import and copy the Network Path. Upload your PST.
Later, create a CSV to map the mailboxes, checkbox the options in the import data window, and click Next.
Finally, upload your CSV, click Validate >> Save to migrate OST file to Office 365.

Apart from this, there is another way to import OST file to Office 365 by the Drive Shipping method in place of Network Upload. But it is a little complex as well. Further, let’s see who this method is useful for and where it falls short.

Best Fit: For users with a few OST files and good technical expertise.

Drawbacks of the Manual Method

The process is too lengthy, difficult, and tiring, especially if you are a new user.
There is a limitation on the size of the OST mailbox you can import with this method.
The formatting and data consistency are issues with this process, as they aren’t retained.
Users may have issues uploading PST, or the network stability can be an interruption.

Therefore, it is necessary to get a professional tool that overcomes these cons. As well as, which can help with: batch export, free conversion, safe and instant import with no loss. We have one similar tool for you that has all the required needs and is mentioned as follows.

Hassle-Free Import OST File to Office 365

OST to PST Converter Software is a top-notch solution for every kind of user who doesn’t have Outlook or does not want to install it. Whether you are a techie or a non-techie, working on Windows or Mac OS, this easy-to-use tool works everywhere and for everyone.

Additionally, it gives support to batch import large OSTs with big attachments at once into the desired Office 365 mailbox with full security. Moreover, the data is intact throughout the process, and you even get to use its demo version with no costs included.

Steps to Feasibly Import OST to Office 365

Launch the software and opt for Select Folder or Select File option, as desired.
Then, click Next and, using the Select buttons again, add your OSTs to the tool.
Press Next, and after that, the tree structure with folders is loaded. Preview and select for your import.
Further, again tap Next, and you can choose the Office 365 client from the email clients menu.
Complete the Sign In process and then, from the tool, select filters and the destination mailbox. Lastly, tap Convert.

Conclusion

The conversion of Outlook Exchange mailbox data in OST to the cloud Office 365 platform seems daunting. But with the methods given above, you can simplify the import OST file to Office 365 in no time. Though the manual method is not suited for all and has a long process, which takes time and effort, it is reliable. But for those who are in a hurry, have large OST data, and need to automate tasks, they must use the dedicated tool.

Frequently Asked Questions

Q. What is the best way to import an OST file into Office 365?

Ans. The best way, if you ask, is none other than the professional SysInfo OST to PST Converter Tool. It streamlines and automates the process while managing large volumes, which in itself is the biggest advantage.

Q. Can I import OST file to Office 365 without Outlook?

Ans. Of course, you can import OST into Office 365 without MS Outlook. For that, you need to launch the OST to Office 365 Import Tool and start following the tool guide above.

Q. Can I directly import OST into Office 365?

Ans. If you work manually, direct import is not possible. But if you utilize the expert OST File Converter, then direct import is done quickly with 100% data accuracy.

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About The Author:

Lovely Baghel

As a content writer, I specialize in Email Migration, Data Recovery, Email Backup, and File Management. I have been writing professionally for two years now. There is so much information available in this field that I am intrigued by the newer technologies and techniques.