Import OST to Office 365 Account: Recommended Solution
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Written By
Aaradhya Jain -
Approved By
Shivam Rathore -
Updated on
February 10th, 2026 - Read Time
5 minutes
User Query: I have an OST file from Microsoft Outlook that contains important emails, contacts, and attachments. My Outlook profile is no longer working, but I want to access this data in Office 365. What is the safest and easiest way to import OST to Office 365 without losing any information?
Summary: Microsoft Outlook stores mailbox data in OST (Offline Storage Table) files when it is connected to Exchange, Office 365, or IMAP accounts. These files allow users to work offline and sync data later. However, problems arise when Outlook crashes, profiles are deleted, or users switch systems. In such cases, OST files become inaccessible. Office 365 (Microsoft 365) is a cloud-based platform that allows users to access email anytime, from anywhere. In this blog, we explain both the manual and a professional DRS OST Converter Tool for hassle-free results.
Why Migrate OST to Office 365?
There are several reasons why users want to move OST data into Office 365:
- OST files cannot be opened directly without Outlook.
- Office 365 offers cloud access and better data security.
- The emails remain safe even if the local system fails.
- Office 365 offers easy access across devices and locations.
- Moreover, simplified email management and backup.
Manual [Free] Method to Import OST to Office 365
The manual approach is only useful when the OST file is connected to a working Outlook profile. It is suitable for small mailboxes and requires careful steps. Steps to Import OST into Office 365 Manually
- Firstly, open Microsoft Outlook with the same account linked to the OST file.
- Make sure Outlook is connected and syncing properly.
- After that, go to File > Open & Export > Import/Export.
- Next, choose Export to a file and select PST.
- Further, export mailbox data into a PST file.
- Log in to Office 365 using Outlook.
- In the end, import the PST file into the Office 365 mailbox.
Limitations: Manually Transfer OST File to Office 365
- Users only use the manual method to import a few OST files.
- It requires Outlook configuration and server connection.
- There is a risk of missing emails during manual export.
- This is not suitable for large or multiple OST files.
- In addition, the manual method is time-consuming and error-prone.
Professional Solution to Import OST to Office 365
To avoid manual limitations, you can directly use the reliable DRS OST File Converter. This tool allows you to convert a single/multiple OST files at once with no data loss. It offers several advanced features, such as Preview, Remove Duplicate, Date Filter, and more. Also, it preserves the original data formatting, structure, and metadata during the entire process. With its simple interface, every user can easily use it without needing any technical skills. Furthermore, you can convert OST File to MBOX Format and other formats, including File Formats and Email Clients.
Simple Steps to Migrate OST to Office 365
- Download and install the DRS OST to Office 365 Migrator Tool.
- Choose “Select Files” or “Select Folder” to add your OST files.
- Then, you can preview and select the OST emails to import. Hit Next.
- Enter your Office 365 Email Address and Password to Sign In.
- Lastly, apply advanced features as per your needs. Click Convert.
Real-Life Scenario: OST to Office 365 Migration
An IT administrator needed to recover employee emails after a system crash. Users deleted the Outlook profiles and left the OST files behind. Using a professional DRS OST to Office 365 solution, the team restored all mailboxes directly into Office 365 without rebuilding profiles or reinstalling Outlook.
Conclusion
In this technical blog post, we discussed several methods to import OST to Office 365. While the manual method works only in limited cases, it is not reliable for most users. A professional solution provides a secure, faster, and accurate way to move OST data into Office 365 without data loss. It ensures business continuity and easy access to important emails. A free version of this tool is available to understand its features and functions.
Frequently Asked Questions
Ans: No, Office 365 does not support direct OST file import. OST files depend on an Outlook profile and server connection. To move the data, users must either export the OST to PST using Outlook (if the profile is active) or use a professional DRS OST to Office 365 migration tool that uploads data directly to the cloud.
Ans: You can import OST data in two ways. If the OST file is connected to a working Outlook profile, export it to PST and then upload the PST to Office 365. If the profile is unavailable or the OST is orphaned, a professional DRS OST to Office 365 tool is the safest option, as it transfers emails, contacts, and attachments directly.
Ans: Office 365 itself supports large mailboxes, but manual methods may fail with very large OST files due to Outlook limitations. A professional DRS OST Converter Tool handles large OST files more efficiently and allows smooth transfer without size-related issues.
Ans: Yes, a professional DRS OST to Office 365 migration tool supports bulk conversion. Users can import multiple OST files at once, apply filters like date range or duplicate removal, and complete the migration without data loss or manual effort.
About The Author:
I, Aaradhya Jain, a technical content writer at DRS Solutions, specializes in delivering clear, practical guides on data management, migration, and recovery tools. With a detail-oriented and user-first approach mindset, I transform complex processes into actionable insights for IT professionals and decision-makers.
