Storing Exchange mailbox data on a cloud platform like Office 365 offers several advantages. Emails and other mailbox items can be accessed anytime and from anywhere, as long as there is an internet connection. Because of this flexibility, many Exchange users prefer to move their offline Outlook data to Office 365 for long-term access and security.

An Outlook OST file contains a local copy of an Exchange mailbox that works in offline mode. To make this data available in Office 365, users need to transfer the OST file to the cloud. This can be done using different approaches, depending on technical expertise and data volume.

Why Users Want to Open OST Files in Office 365

There are several common reasons for migrating OST data to Office 365, including:

• Moving to Office 365 to take advantage of its cloud-based features
• Recovering mailbox data after Exchange server failure or corruption
• Reducing dependency on Exchange server maintenance and downtime
• Accessing data quickly and securely after accidental deletion

Methods to Open Outlook OST Files in Office 365

Currently, Microsoft does not provide a direct way to upload OST files into Office 365. However, users can still migrate OST data by following alternative methods.

Method 1: Convert OST to PST and Import Manually

In this approach, the OST file is first exported to PST format. After conversion, the PST file can be uploaded to Office 365 using Microsoft’s import options. While effective, this method can be time-consuming and requires technical knowledge.

Method 2: Use an Automated OST to Office 365 Tool

Professional third-party tools allow users to move OST files directly into an Office 365 account. These tools simplify the process, reduce manual effort, and help maintain data accuracy during migration.

Manual Method to Save an Outlook Offline OST File in Office 365

The manual approach to opening an Outlook OST file in Office 365 follows an indirect process. Since OST files cannot be uploaded directly to Office 365, they must first be converted into PST format. Once the PST file is created, it can then be imported into the Office 365 cloud environment.

This method involves two main stages: converting the OST file to PST and uploading the PST file to Office 365.

Step 1: Convert OST Data into PST Format

There are several built-in ways in Microsoft Outlook to export OST data as a PST file.

Method 1: Create a New PST and Copy Mailbox Data

This option allows you to manually move mailbox items into a newly created PST file.

·        Launch Microsoft Outlook on your system

·        Create a new PST file within Outlook

·        Select the required mailbox folders from the OST file

·        Copy the selected items and paste them into the new PST file

Method 2: Use Outlook’s Archive Feature

Outlook provides an archive option to store mailbox data locally.

·        Open Outlook and navigate to File > Cleanup Tools > Archive

·        Choose the folders you want to archive

·        Select a destination location and confirm the process

Note: This method does not support exporting Outlook contacts.

Method 3: Export OST Data Using Outlook Export Option

Another way to generate a PST file is by using Outlook’s export wizard.

·        Open Outlook and go to File > Open & Export > Import/Export

·        Select Export to a file and click Next

·        Choose Outlook Data File (.pst) and continue

·        Select the mailbox folders, choose a save location, and complete the export

Note: This option is only available when Outlook is connected to an active Exchange account.

Step 2: Upload the PST File to Office 365

After converting the OST file into PST format, the next step is to move the PST file into an Office 365 account. Microsoft offers two ways to do this.

Method 1: Network Upload Using Azure AzCopy

This method uploads PST files to Office 365 through Microsoft Azure.

·        Install the Azure AzCopy tool on your system

·        Use the Shared Access Signature (SAS) URL to authorize the upload

·        Create a PST mapping CSV file

·        Set up an import job in Office 365

·        Start the upload and monitor the import process

Method 2: Drive Shipping to Office 365

Drive Shipping is an alternative option for large data transfers.

·        Copy the PST files to a physical hard drive

·        Ship the drive to Microsoft as per their instructions

·        Microsoft uploads the data directly to your Office 365 tenant

OST to Office 365 Converter – An Automated Solution to Open OST Files in Office 365

Migrating Outlook OST files to Office 365 can be challenging, especially for users without technical expertise. The process involves multiple steps and often becomes complicated when dealing with large or inaccessible OST files. Because of this, professional third-party solutions are commonly recommended for a smooth and direct migration.

The OST to PST Converter offers a straightforward way to resolve the common concern of opening Outlook offline OST files in an Office 365 account. The tool enables users to selectively transfer mailbox data from OST files to the Office 365 cloud without interruptions or data integrity issues. Its simple interface makes it suitable for both IT professionals and non-technical users.

This software supports all major Windows operating systems, including Windows 10, and allows both single and bulk OST migrations in one streamlined process. Whether you need to move one mailbox or several OST files at once, the tool handles the task efficiently. To help users understand its functionality, a free demo version is available that allows exporting up to 20 items per folder to Office 365 at no cost.

Conclusion

In this article, we discussed multiple approaches to open Outlook offline OST files in Office 365. Users can choose a method based on their data size and technical comfort level. The manual approach may be suitable for migrating a small number of OST files, but it requires time and technical knowledge. For large-scale or business-level migrations, an automated OST Converter solution provides a faster, safer, and more reliable alternative.