Import OST Data to Office 365 with Attachments in 2026

Why Organizations Should Migrate OST File to Office 365?

• Access mailbox data from anywhere using a cloud-based platform.
• Recover important emails stored in offline OST files.
• Centralize business communication within a single environment.
• Protect mailbox data with Microsoft’s advanced security features.
• Eliminate dependency on old Exchange servers or Outlook profiles.
• Simplify mailbox management through a centralized admin portal.

Standard Procedure to Import OST File to Office 365

Generally, there is no direct method to transfer OST files into Office 365. However, there is an indirect route that involves two steps. Follow the steps below:

Step 1: Convert OST to PST

1. Firstly, make sure that your Exchange OST file is present in Outlook.
2. Then, go to File, and in the left side options, click on Open & Export.
3. In the displayed options, select the Import/Export icon.
4. Further, in the new dialog, select Export to a File. Click Next.
5. Pick for Outlook Data File (.pst) and again tap Next.
6. From the import folders list, select OST files/folders. Hit Next.
7. After that, press Browse and search for a location to save the PST file.
8. Lastly, click the Finish button to convert the OST file to PST.

Step 2: Import OST to Office 365 After PST Conversion

1. Start Office 365 Exchange Admin Center and choose Permissions.
2. Later, press on Organization Management >> + >> Mailbox Import Export.
3. Then, click Add >> Ok >> Mailbox Import Export >> Save.
4. Now, move back to Admin Center and press Setup >> Data Migration >> Upload File >> New Import Job.
5. In the dialog, enter the name and import description. Click Next.
6. Subsequently, enter the date and click Next. You will get a SAS URL. Copy it.
7. Next, download and run the Azure AzCopy Tool and provide the Network Path to import. Click Enter.
8. Once the PST file is uploaded, create a CSV to map the PST file with M365 accounts.
9. The Import window opens, select the options, and click Next.
10. At last, Select Mapping File >> Upload CSV >> Validate and click Save.

Why Does This Method Fall?

• The process is tiring and complex and needs technical expertise.
• High data loss is possible with no recovery options.
• Cannot bulk migrate OST files and complete mailbox data.
• Requires a connection with the Exchange Server the whole time.

Comparison Between the Manual and Automated Solution

End-to-End Solution to Import OST File to Office 365

SysInfo OST File Converter Pro gives IT professionals a straightforward way to export data from OST files without requiring any Exchange server access. Emails, contacts, calendars, tasks, & journals are extracted and saved in multiple file formats. Enterprises handling large OST datasets can also use the tool to import OST to Google Workspace. A Date Range Filter helps narrow down the extraction to specific time periods. Also, there is a technical support team available to solve your query 24*7.

Exclusive Features of SysInfo OST to Office 365 Converter

• Processes multiple OST files in a single operation.
• Uses Date Range Filter for selective data conversion.
• Previews mailbox data before starting the conversion.
• Searches and exports specific emails or folders.
• Help to import OST file into Windows Live Mail and other clients.
• Generates detailed conversion and processing reports.
• Preserves folder hierarchy and email metadata.
• Handles large OST files without size restrictions.
• Compatible with all major Windows versions.

Steps to Import OST Offline Files into Office 365

1. Download the OST Converter Pro Software.
   
2. Then, add your OST file or folders and click Proceed.
   
3. Further, select and preview files to import and hit Proceed.
   
4. After that, choose Microsoft 365 and sign in with its credentials.
   
5. Lastly, use migration filters and click Start Export.
   

End Note

The SysInfo OST File Converter Pro provides a direct path to import an OST file to Office 365. The tool processes OST files of any size, preserves the complete folder hierarchy, & delivers a verified migration with zero data loss. IT administrators managing multiple accounts can execute the entire process in bulk, reducing migration time significantly. For any enterprise or individual looking to import OST file to Office 365 after an Exchange server becomes unavailable, this utility remains a reliable and audit-ready solution.

Frequently Asked Questions

About The Author:

Lovely Baghel

Lovely specializes in technical writing for SysInfoTools Software and has over 2 year of experience writing blogs, and articles about databases & backup, email recovery, email migration & management solutions. Her passion is researching and developing content that helps Office users, professionals, administrators, enterprises, and novices solve multiple problems.