USC Inc. Successfully Migrates Mailbox Data From OSTs To Office 365


United Software Consultants, Inc. – Software Development and IT Services Company in New Jersey, United States

Business Need

Extract crucial mailbox data from large OST files for migration to Office 365


Stellar Converter for OST

"Our goal of OST to PST conversion was successfully accomplished. Thank you"

Aijaz Abbas - President,

IUnited Software Consultants, Inc.

  Download Case Study

United Software Consultants (USC) needed to migrate thousands of Outlook mailboxes from its on premise Exchange server to Office 365. It was able to migrate most of the mailboxes except the mailboxes associated with legacy users (former employees) who had moved out of the organization. The data associated with these deleted/archived mailboxes was available as OSTs, which was inaccessible 'as is' and therefore posed a challenge to the migration process.

These OST files — nearly 18GB in size — were stored on local drive and contained crucial information which would be permanently lost unless a viable solution would extract the data in readable PSTs. USC realized the need and decided to act fast for mapping and migrating all the existing and archived user profiles to Office 365 within the planned timeline.

USC is a software development and IT services company which does web, mobile, and cloud app development. Based in the US, it has been serving small and large enterprises in various verticals since 1988.

USC needed to migrate its entire org-wide mailboxes from the on premise Exchange Server to Office 365, which required user profile creation, mapping, and migration for thousands of Outlook users.

Business Challenge

USC faced 3 key challenges:

  1. Extracting business-critical data from inaccessible OSTs
  2. Avoiding OST file corruption, while extracting the data via manual procedure
  3. Achieving faster turnaround to meet the mailbox migration timelines

OSTs become oversized with time, and that's what happened in case of USC. Tenured users who had left the organization had their mailboxes deleted but the respective OSTs — which were over 18 GB in size— were still available on the local drive.

Given the fact that Exchange Server stores the disconnected mailbox data for 30 days and these legacy OSTs were well beyond this cut off time, it was evident that the data was flushed off the server.

The only way to get access to this data was to extract it from the OSTs.

The USC team contemplated manual procedure to convert the OSTs into PSTs and extract the data but it was obviously time consuming and laborious.

Also, the stakes of losing the data to file corruption were too high, which was likely due to the massive size of these OSTs. Considering the limitations of manual procedure, USC decided to explore a more specialized solution for this problem.


The USC Exchange admin -leading the mailbox migration project -decided to take the software route for addressing this problem. The primary goal was to attain 100% migration of mailboxes (including the data stored in OSTs) to Office 365, without any glitch and in the shortest lead time. Also, the solution was expected to work fast with minimal assistance.

With much deliberation, USC chose to go with Stellar Converter for OST software (Technician Edition) to convert the OSTs into PSTs. The tool allowed them to convert and extract all the inaccessible OST files and the components- email attachments, contacts, calendars - to PST files. The Technician edition further offered the advantage of directly exporting the extracted mailboxes to Office 365, which helped with efficiency and convenience.

Execution Approach

  • Downloaded and installed Stellar Converter for OST Technician edition
  • Opened the OST file in the software.
  • Scanned the file, which displayed a preview of the mailbox items
  • Selected specific mailbox items to be converted
  • Selected 'Export to Office 365' to move the converted mailboxes directly to Office 365
    • A dialog box to enter Office 365 login credentials opened
  • Entered the Office 365 login credentials (email ID & password) to complete the process


USC achieved 100% migration of all the mailboxes -including the data stored in OSTs -to Office 365, with minimal monitoring and manual intervention. Also, the overall migration process was completed within the stipulated timeline. The OST to PST converter software also helped USC to restore the deleted mailboxes data from the OST files, without any risk of file corruption.

Key Benefits

  • 100% data extraction: All the mailboxes and individual components were extracted from the OSTs in original form, ready for access and export to cloud.
  • Risk free conversion: Considering the huge size of the OSTs and possibility of corruption, the tool successfully performed the entire conversion process without any problem.
  • Quick and Simple: The entire mailbox conversion procedure was done in a few clicks, without the need for any manual intervention or monitoring. This freed up the administrator's capacity and helped attain the outcome in tandem.

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