Import Offline OST to Office 365 in a Professional Way

Updated On - January 11, 2024 by Armaan | Reading Time: 9 minutes

With Exchange Online, businesses can benefit from Exchange Server’s advanced features without installing the server on-premises. Exchange Online can be accessed by those who subscribe to Microsoft 365’s Business or Enterprise Editions, including the service. The ability to purchase licenses for the number of expected users is a great perk of a Microsoft 365 subscription. It is available for purchase separately or as part of Microsoft 365, which fully integrates with the rest of Microsoft Office. Also, Microsoft 365 provides all-time accessibility and user-oriented subscription plans with no downtime hence users import offline OST  to Office 365.

You may get confused because you can open an Outlook account in Office 365 and get all your OST file data to Office 365. OST is Microsoft Outlook’s file format used to store data on the server. However, with Office 365 trend, and Office 365 including Outlook, users want to import their old OST files to Office 365. But what if the OST files are corrupt and offline? How will you import offline OST to Office 365?

In this write-up, we’ll look for the same, but before that, let’s identify the scenarios which raise the need to import Offline OSTs.

Why is the need to import Offline OST to Office 365?

Having Outlook OST files in the cloud can provide several benefits; you can access OST file data at any and anytime. We all know Office 365 is a cloud platform accessible worldwide and on any device such as Mac, iPhone, Android, or Desktop, you name it.

Apart from this, there can be several scenarios for which you may need to import Offline OST to Office 365, such as:

  • Your organization have moved to the Cloud server, and you want to keep your data.
  • Some of your colleagues or clients use Office 365 with whom you need to share your Offline OST files data.
  • Also, by moving your OST to Office 365, you can replace your server’s hosting and maintenance charges, as Office 365 is cloud-based and doesn’t need any installation.
  • Also, office 365 allows you to access your device on multiple devices simultaneously. So it is a good move to import offline OST to Office 365.
  • Last but not least, almost every Office 365 user who has shifted from Outlook has admitted that Office 365 is more convenient and advanced than Outlook.

Now you’re aware of the scenarios and benefits for which you might need to import your Offline OST to your Office 365 mailbox. Now move to our main heading of the article, which is how to take your OST files (Orphaned and corrupt) to Office 365.

Manual Method to import Offline OST to Office 365

The OST files must be converted to the PST format first. At that point, we transfer the PST files to Office 365. After converting OST files to PST format and uploading them to Office 365. This is a roundabout approach to importing OST files into Office 365.

Phase 1: Change the File Format from OST To PST.

  1. Launch the Outlook email client. Navigate to “File” and then “Import and Export.”
  2. Click “Export to a file” and then “Next” to export the data to a file.
  3. When prompted, select “Personal Folder File (.pst)” and then “Next.”
  4. Click “Include Subfolder,” choose the email or folder, and then “Next.”
  5. Select a destination on your computer’s hard drive, tick the box labelled “Replace duplicate with items imported,” and press “Next.”
  6. You can enter a password (if you choose) or just click “Ok.”

Please note that the stated method will not work if the Exchange server is down or unable to connect to the server. So, if you need to convert OST files to PST format, utilize the Regain OST to PST converter; it has many benefits, which I’ll tell you in the end.

Phase2: Import your PSTs to the Office 365 cloud

  • To access Exchange after logging into Office 365, navigate to the Admin Center.
  • Now, double-click “Organization Management” under “Permissions.” a window labelled “Exchange Admin Center” (EMC) will load. When the new window opens, choose “Mailbox Import Export” by clicking the plus symbol. After selecting “Add,” confirm by selecting “Ok.”
  • Again, choose “Mailbox Import Export” and click “Save.”
  • Click “Upload file” under the “Admin Center,” “Setup,” “Data Migration,” and “Upload” menus.
  • Later, after naming the import job, select “New Import Job” and proceed from there.
  • Click “Upload Your Date” and “Next” to go to the next step.
  • Select “Show Network Upload SAS URL in the new box,” then copy the URL and paste it into the notepad.
  • Acquire the Azure AzCopy here. When you click “Run,” the programme is automatically set up.
  • To import a PST file into Office 365, you must first allow access to the folder or file in question and then copy its Network Path.
  • Open the Microsoft Azure AzCopy tool and type: AzCopy.exe /Source: Network Path or File location /Dest: “SAS URL”/V: location path where you wish to save the log file /AzCopy.log /Y,

Sample Code:AzCopy.exe /Source:\DESKTOP-MPKVU38UsersleDesktopImport /Dest:”” /V:c:UsersleDesktopAzCopy.log /Y

  • Once the PST file has been uploaded to the mailbox account, a CSV file will need to be created to map the PST file into the mailbox account.
  • Click “Next” in the import data window after checking both boxes.
  • Select “Upload CSV file,” then “Validate,” then “Save,” and finally “, Select Mapping file.”

At last, your PST file will be successfully imported to Office 365. Hence, you’ve successfully import offline OST to Office 365.

Limitation of manual approach

So it was the manual process to import your OST files into Microsoft 365 mailboxes. As you can see, the process is lengthy and maybe a walk on eggshells. Apart from this, if you’ve multiple Offline OST files to import, don’t even think about it; it will take a lot o time.

Also, all users are not technically sound; hence many users may find it very tough and face issues using it. Chances of human error are also there; hence professional users may find that it is not their cup o tea. Regain Software has developed a professional solution to provide a handy solution for OST to Office 365 migration.

Free Download100% Secure Buy NowPrice: $39

The tool effectively keeps your files hierarchy and Integrity with a 0% chance of data loss. Also, the tool offers a convenient GUI that makes it the best option for newbies and businesspersons. It is a fast and advanced tool with multiple features and advantages. Let’s know what it offers.

Some Prominent Features of Regain OST to Office 365 Migration Tool:

  • Users can add and migrate multiple OSTs to Office 365 migration. OST to Office 365 Migration Tool is capable of batch migration.
  • The tool migrates complete mailbox data, including contacts, calendars, notes, tasks, and emails.
  • There is a restriction on the size of OST files. It is capable of importing offline OST to Office 365 regardless of size.
  • The tool properly maintains the folder hierarchy and data structure and metadata properties.
  • You can have a preview of the OST content before migration. Here you can also see the attachments. It helps users to ensure the data.
  • It supports multiple languages in migrating multiple OST files to Office 365.
  • Regain OST to Office 365 Migration Tool allows resuming the process if paused.
  • Filter facility is also available within the tool as you can easily apply the date range for filtering.
  • Along with migrating to Office 365, this tool can also migrate into Live Exchange.
  • No technical expertise is required to run the tool; very user-friendly GUI.
  • A trial version for no cost is also available to download and use.

Let me describe its step-by-step process so you can install free software and check its features and compatibility with your scenario.

Import Offline OST to Office 365 in just few easy steps:

  • Install and open the free OST to Office 365 Migration tool.
  • Click on the Open option from the ribbon bar.
  • Now add OST files to import into Office 365.Regain OST to Office 365 Migration tool
  • Now, you will be able to preview OST file items.step 4
  • Click on the Cloud Migration option at the top.
  • Choose Office 365/Exchange Server option.
  • Connect with Office 365 by entering the asked credentials.step 8
  • Now, the tool starts to import Offline OST to Office 365.

As you can see, importing Offline OST files into Office 365 is a cakewalk with Regain OST to PST converter.

So what are you waiting for?


With time, technology changes and hence need to change. Office 365 is becoming a popular platform day by day, and users are migrating data from different file formats to Office 365. Outlook users are looking for an efficient way to import Offline OST to Office 365 for the same purpose. For the same, I’ve mentioned two methods one is manual, and another one uses a third-party automated tool. Now it’s up to you what you choose. Remember, whatever you choose, choose according to your need and ease. Also, you must download the free demo version and get ensured that the software’s working.

Frequently Asked Questions

Q1. What possible issues can a user face while using a manual approach?

A. Manual ways are indirect approaches to import offline OST to Office 365. Users may find it very technical as well as lengthy. Also, manually there is a limitation on the size and number of OST files for the migration. Users may have to compromise with the resultant data in Office 365.

Q2. Can I add and import multiple OST files to Office 365 using Regain OST to Office 365 Migration Tool?

A. Yes, you can import multiple OSTs using the Regain migration tool. There is no restriction on adding and migrating multiple OST files. Also, there is no limitation on the size of the OST files. The tool perfectly handles numerous OST files of large sizes.

Q3. Will this tool import all the items present in the mailbox?

A. Yes. This tool migrates all the items present within the OST files. This professional utility can easily migrate emails, calendars, contacts, tasks, and events.

Q4. I am using Windows 11; will this tool be compatible with this OS?

A. Regain OST to Office 365 Migration Tool is compatible with all the versions of Windows OS. So, it doesn’t matter what OS you are using; it will work with all.

Q5. I have some of the OST files that are corrupt and inaccessible. Can this tool handle corrupt OSTs too?

A. This tool is capable of handling corrupt OST files. Firstly, it scans and repairs the corrupt OST files and then proficiently imports offline OST from Office 365 to Office 365. If you have corrupt OST files and want to migrate them to Office 365, this tool will be very handy.

Q6. Do I need to install Outlook to use Regain OST to Office 365 Migration Tool?

A. No. Having Outlook installed is not mandatory or required to use Regain OST to Office 365 Migration Tool. The tool works independently; hence installation of Outlook keeps the same. If you have OST files, you can import offline OST to Office 365.

Q7. How different is the free version from the licensed version?

A. The free demo version is just a restricted version of the fully licensed version. The demo version allows migrating the 30 items per folder as it is meant to provide a demo. With the full licensed version, there are no such limitations.

Author: Armaan

Hello I have been working in Regain Software for the last 6 months. I have been in the field of writing for many years and worked with many Data recovery companies. Here I am writing technical blogs, Software User Guides and manual methods for email conversion and cloud migration. Now, working on all products of our company. Thanks you

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