Learn the Methods to Import OST to Office 365 Easily

Import OST to Office 365

Published By Siddharth Sharma
Anuraag Singh
Approved By Anuraag Singh
Published On October 20th, 2023
Reading Time 10 Minutes Reading
Category General

All accounts configured on an IMAP configuration within the Outlook email client use the OST files by default. However, with the rapid advancement in the cloud infrastructure of Microsoft 365, many users are looking to import OST to Office 365 ASAP. The biggest hurdle to this task is the absence of a native method. That is why we highlight some of the workarounds for this problem in this tutorial. Moreover, towards the end, we also have a sure-shot utility that directly moves all OST files to the desired location. Let’s start by discussing some situations where we need to shift OST files.

Scenarios in Which to Import OST Files to Office 365

Here, we address some of the most common user queries that arise during the migration of OST files.

“I recently got a Microsoft 365 subscription. Now I want to shift my OST files to the new Office 365 environment. However, there are no clear-cut instructions for doing so. Can you help me out?”

Here, a user wants to move their OST files, but they found that Microsoft itself does not provide any mechanism for doing that. The reason is that OST files have direct syncing capability. You may ask how that relates to the import of Outlook OST to Office 365. Well, there is a risk that while importing a new OST file, it overrides the original data. 

“We recently shifted our operations to the cloud and chose Microsoft 365 as our vendor. Some of my employees are complaining that they cannot access their OST file data on their Office 365 accounts. Moreover, due to this, the entire migration operation is now in jeopardy. Is there a way out?”

In this particular scenario, the problem stems from the fact that each OST file has a hidden identifier. This identifier also acts as a key, which only allows the original account to open the file in the same environment. Upon migration to the cloud, the internal IDs must have changed, which is why OST files are not being recognized and refuse to open.

“An old employee just left our organization. Due to regulatory concerns, we have to keep their data in a secure location. The problem is that most of their emails are in OST format and are now in an orphan state. We cannot access them Please provide a solution.”

We suggest you convert the file to PST and move it to the archive.

Import OST Files to Office 365 using Different Manual Methods

When we talk about the manual methods for migrating OST data, we come across three different methods. Here we provide the gist of the methods and their limitations, so you can make the correct decision on your own.

Also Read: Find Out How to Create an Admin Account in Office 365 Effortlessly

The two methods are part of Microsoft’s own import mechanism. Before we can use them, users must know that the method works only with PST files. Therefore, users must do the conversion on their Outlook email client. If you don’t have it, no need to worry about that; the OST to PST converter is a better alternative anyway.

If you have the equivalent PST with you, then move ahead with either of the two methods.

Drive Shipping: In this, you load all the data on a secure physical storage device and mail it to the nearest Microsoft data center. Once the package reaches the data center, a Microsoft employee uploads it to your account.


  • Orphan OST files can’t be transferred. 
  • Spend a dollar for every 500 MB of data. 
  • Purchase brand-new and secure hard drives.
  • Excessive waiting times for the process to complete.
  • Place trust in third-party agencies for shipping critical data.

Network Upload: Here you establish a high bandwidth connection between the cola environment and the Office 365 cloud. After that, you send in the data one user at a time.


  • Limited scalability during large imports.
  • Requirement of a new Azure storage account.
  • Admin needs to establish a high bandwidth connection.
  • Uploading and monitoring are entirely up to the IT admin team.
  • Lacks advanced import filters and features required for complex transfers.

Drive Shipping

This complicated method is divided into different stages for easier understanding. Let’s start with the prerequisites first.

Stage 1. Preparation for the Drive Shipping Method

  • Mailbox Import Export and Mail Recipients must be applied to the admins at source and target, respectively.
  • If the PST files are too large, split them
  • Encrypt hardrive with bitlocker
  • Choose the partnered shipping service in your geography

Stage-2. Get the PST Import Wizard

  • Visit the Purview Compliance Portal and set up a new import job.
  • From the import data page Download and install the WaImportExportV1.zip file.

Stage-3. Prepare the Hard Drives

  • User must get hard drives that are both encrypted and Compatible with Office 365
  • Then, using a command prompt, visit the directory where WaImportExportV1 exists.
  • Type in the following Command:
WAImportExport.exe PrepImport /j:<Journal File Name> /t:<Drive Letter> /id:<Session Name> /srcdir:  file Location> /dstdir: <File path of PST> /blobtype: BlockBlob /encrypt /logdir: <Location of Log file>
  • Modify this Command as per your Specific Use case.

Stage-4. Build Import Mapping to Import OST to Office 365

  • It is a CSV file having Distinct Parameters in the header row.

Stage-5. Build an Import Job for Office 365 

  • Log in to the Azure portal, and go to Data lifecycle management’s Import section.
  • In the import job, go for “Ship hard drives to one of our physical locations” option.
  • Acknowledge the fixed terms and conditions and choose the hard drive location.
  • Add a journal file to each drive and ‌attach the mapping file to validate the data.

Stage-6. Ship Hardrives to Microsoft Datacenter

  • Pack the drives and ship them to the nearest Microsoft data center.
  • Follow shipping instructions, including tracking number specification, etc.
  • Only when the hard drive reaches the data center, you can start an import job.

Network Upload

Like the Drive shipping method network upload is also equally complicated if not more. As a result, we have split it into separate stages too.

Stage-1. Set Azure AzCopy & Find the SAS URL

  • Sign-in to Microsoft’s Compliance portal with admin-level credentials.
  • Go to the left side pane and look for Data lifecycle management menu.
  • Below it, pick Microsoft 365 option and click on import, then click on + symbol.
  • Screen pops up with two options ship or upload; select Upload.
  • Users need their SAS URL and install Azure AzCopy transfer tool.

Stage-2. Import Converted OST to Microsoft 365

  • Start Uploading your PST files by using this Command.
azcopy.exe copy "<Location of Source PST files>" "<SAS-URL>"
  • Command needs modification in most cases.

Stage-3. PST Files Viewing and Preparation

  • Confirm that the PST files are in a Compatible format. 
  • Verify if they remain in a specified folder within the Azure blob.

Step-4. Build an Import Mapping for the PST Files 

  • It is a CSV file with different Parameters in its Header row.
  • Create it Manually Or download a Copy from Microsoft’s Official site.

Stage-5. OST to Office 365 Import Job Creation

  • Generate a new PST import job in the Office 365 Security & Compliance Center.
  • Specify all parameters such as ‌Location, Mapping Options, and Import Settings.

Each of the above-mentioned methods has one limitation or the other. Therefore, it is recommended to go for an alternative approach.

Automated Utility to Shift OST Files to the Cloud

None of the manual methods come close to what the professional SysTools OST Import tool offers. From the get-go, users walk into a seamless and easy-to-operate UI. Behind the surface, there are state-of-the-art algorithms working tirelessly to import OST to Office 365 at breathtaking speeds. All of this is packaged in a one-time purchase bundle with lifetime usage.

Download Now   Purchase Now

If this doesn’t convince you, then we present some of the unique advantages of the tool.

  • Facilitates the Import of Hosted Exchange OST Files to an Office 365 Account
  • Seamlessly Transfers OST Mailbox Items, Including Emails, Contacts, Calendars, Tasks, and More
  • Effortlessly Imports OST Files to Office 365 User or Admin Accounts
  • Enables Selective Import of OST Data Using the “Date Filter” Option
  • Offers the Choice to Preserve Folder Hierarchy Throughout the Import Process
  • Maintains Metadata Properties, Such as Sender, Recipient, Cc, and Bcc, in Office 365
  • Converts OST Files from IMAP, Exchange, Hotmail to Office 365 OWA Accounts
  • Supports the Import of Corrupt and Password-Protected OST Files to Office 365 Mailboxes

Also Read: Learn About the Office 365 Mailbox Types and their Uses

With these features, you must be eager to try out the tool yourself. So to make things easier, we provide the instructions right here. Just hop on to the next section and find out for yourself.

Steps to Run the Utility

Step 1. Download and Open the utility on your desktop then click on Add File button to pick the OST file to be imported to Office 365.

Step 2. Hit the Office 365 radio button to import the OST file to the Microsoft 365 mailbox, type the Destination for migrating the OST file, and press the Next button.

Step 3. In the screen that pops up type in the Office365 credentials then Validate the Office365 account and press the Export button.

Step 4. Let the tool complete the import after which you are free to view your data on the destination Office 365 account.


In this article, we went from discussing the reasons to import OST to Office 365 to elaborating on all available manual methods. Moreover, we saw how difficult and ineffective the manual methods were. As a result, we also gave a directive on how to use the industry standard OST import tool. All those who opt for the tool can shift their OST data in the shortest possible time.


Q. A file conversion like that of OST to PST has a chance of data loss; is there no alternative way of importing OST files that can bypass the conversion entirely? 

Ans. Of course, there is just use the automated utility provided above and directly move all OST files without worrying about data loss.

Q. What is the major difference between OST and PST file formats?

Ans. OST and PST are both proprietary file formats used within Outlook as a primary means of email storage. The key area where they differ from each other is the protocol that they work on. PST works if an account is set on POP3, while OST is used in the case of IMAP. 

Q. Why is interconversion not allowed between PST and OST?

Ans. It is not exactly forbidden by Microsoft, but it is not recommended. This is because PST and OST work in fundamentally different situations. The former stores a copy of all server information locally. OST has a constant sync enabled, which reflects all changes from one end to the other.

Q. Can an orphan OST file be imported to the Microsoft 365 cloud?

Ans. Usually, data in orphan OST files is as good as gone, but there is no need to fear if you have the above-mentioned professional tool. It is capable enough to move even isolated OST files.

Q. I have many OST files, and some of them have corrupted data. Is there a quick and easy way to recover the data?

Ans. The software that we have so thoroughly discussed can transform even corrupt OST files back to working condition. Apart from this, you can also import all the OST files to a new account using the same tool.