How to Import OST to Office 365 with Attachments


Written By
Suman Rawat

Updated on
February 1st, 2023

Summary:- Outlook automatically creates an OST file to store mail items if you use an Exchange,, or IMAP email account. In contrast to PST, OST files are encrypted and cannot be imported directly into Office 365. Hence, this article will teach you how to import OST to Office 365 step-by-step. Additionally, you'll learn about an OST to PST converter tool that allows you to import OST files to Office 365 in bulk.

What is MS Office 365?

The best Microsoft cloud service currently available is Microsoft 365. It has hundreds of millions of users globally and brings Microsoft the greatest profit. Even though Exchange Server is the main email server used by enterprises, Exchange Online, a Microsoft 365 Enterprise and Business feature, offers greater flexibility for email access globally.

Microsoft Outlook is the preferred email client for sending and receiving emails when accessing Microsoft Exchange Server email. You may use it to manage your calendar, store contact information, send and receive emails, monitor tasks, and record names and phone numbers. However, Office 365 is a better choice if you compare both email clients' benefits. Hence, let’s get aware of some of the advantages of MS Office 365.

Benefits to Import OST to Office 365

Office 365 is a full-featured online office suite with well-known programs like Word, Excel, PowerPoint, Outlook, and OneDrive. Here are a few of the qualities that make it so well-liked.

  • Sharing data, including documents, presentations, and images, is one of the main benefits of Office 365 for Business subscribers.
  • Additionally, since your data is stored in the cloud, you can view, modify, and print them from any location.
  • Working together on projects with your coworkers is made easier by the ability to share papers online.

There are various reasons why OST files might need to be imported into Office 365 accounts. The best and easiest way to upload an OST file to an Office 365 mailbox will be covered in this post.

Popular Methods to Import OST to Office 365

There are various methods to open an OST file in Outlook 365, but here we will explain the most popular and simplest one. So let’s move ahead to learn the procedure for these methods.

  1. Import OST to Office 365 Using Outlook
  2. Directly Import OST files to Office 365 Using third-party software

Method 1: Upload OST to Office 365 Using Outlook

There is no direct manual method to save OST file into Office 365, but don’t worry, here we will explain an indirect procedure. In this method, first you need to convert OST to PST, then upload the converted OST file to O365.

Step 1: Convert OST to PST Using Outlook Features

There are two techniques to export OST to PST, here we will describe both of them, so let’s continue:

Technique 1: Use the Import/Export Feature of Outlook

  1. Login into your MS Outlook account.
  2. Go to Open File » Open & Export » Import/Export.
  3. Select the Export to a file option and then press Next.
  4. Choose Outlook Data File(.pst) option and hit the Next button.
  5. Select the folder you want to convert and click Next.
  6. Press on the Browse button to assign a saving location to your resultant file.
  7. Click on Finish to initiate the conversion process.

Technique 2: Use the Archive Feature in Outlook

  1. Open your Outlook account.
  2. Go to File >> Tools >> Clean up old items.
  3. Select the folder that you want to archive.
  4. Open Browse to set a destination path for your output file.
  5. Lastly, click Finish to complete the process.

Both of the above-outlined techniques can convert your OST files into Outlook PST. Now let’s move to the next step.

Step 2: Upload PST File to Office 365 Using MS Outlook

In this step, there are two procedures that you need to follow, as mentioned below.

#1 Sync your Office 365 Account in Outlook

  1. Launch Outlook on your system.
  2. Go to File>>Add Account.
  3. Now, submit your Office 365 email address.
  4. Provide your Office 365 account password and re-enter the password.
  5. Click on the Next button.
  6. Make sure you also log in to your Office 365 account on the browser.
  7. At last, you will receive a message of successful Configuration.

#2 Import Outlook PST emails to Office 365

  1. Again run Outlook on your PC.
  2. Go to File>>Open & Export Option.
  3. Pick the Import/Export feature.
  4. Choose the Import from another program or file option and then click Next.
  5. Select Outlook data file(.pst) and click Next.
  6. Click on the Browse button to add the PST file that you want to import>>Next.
  7. Select the configured Microsoft Office 365 account from the drop-down menu.
  8. Click on the Finish button to import emails from Outlook to Office 365.
  9. At last, your Outlook PST emails are migrated into your O365 Account.

By following the above-outlined procedure, you can get the answer to “How to import OST file in Outlook Office 365” manually. However, this method is lengthy and complex, and not suitable for the non-technical. To solve this issue, we have developed an outstanding automated tool for fast and direct migration of OST files to Office 365.

Method 2: Directly Import OST to Office 365 - A Professional Solution

The OST to Office 365 Migration Tool is the ultimate tool for personal and business users to accurately and precisely import OST files into Outlook 365. The software is capable of transferring all the information from the OST file to Office 365, including emails, attachments, contacts, calendars, etc. It is highly efficient in maintaining data integrity and hierarchy.

  1. Download and Run the OST to Office 365 Migrator.
  2. In this wizard, select Single file or Multiple files.
  3. Now, click the Browse button to add the OST files to import.
  4. Select the OST files that you want to import and click Next.
  5. Pick Office 365 from the drop-down menu.
  6. Here, enter your O365 login credentials.
  7. Utilised the given features of the software such as Remove Duplicate Items, Mail Filter, etc.
  8. Click the Convert button to migrate OST to Office 365.


In this article, we have explained the most popular ways to import OST to Office 365. There are two methods, one manual and the second professional, you can choose any of them as per your requirements. However, the manual procedure has many limitations that can lead to various problems. Therefore, we suggest you use the automated solution to avoid any misfortune and to migrate OST files to Office 365 in bulk.