Introduction
A sudden crash of Exchange Server can create critical email recovery challenges for an IT department. Outlook OST files have mailbox data cached locally, but employees don't always easily access that information after a server failure.
This case study is based on a real-world recovery situation where a mid-sized IT services firm suffered an unexpected Exchange Server failure. The company’s infrastructure team was busy rebuilding the server and the company needed to recover important emails, contacts, calendars and other mailbox information from locally stored OST files.
The Problem
The company was an IT services firm with about 185 employees in two locations. Internal communication was very much Microsoft Outlook based. Outlook was connected to an on-premise Exchange Server.
One Monday morning, the Exchange Server failed due to a storage controller failure. The database could not be brought online immediately and some employees were unable to access their regular mailboxes.
The IT team had recent backups of the servers, but restoring the entire Exchange environment would take several hours. Employees also said they wanted to see project discussions, customer correspondence, schedules and meeting contact information.
The team discovered that many of the workstations had local OST files created by Outlook Cached Exchange Mode. Cached Exchange Mode keeps an up-to-date copy of mailbox information on the user’s computer, according to Microsoft. OSTs are typically tied to their Exchange account and cannot be used as a portable PST archive.
Project Statistics
Impacted Employees: 185
Found OST files: 142
OST data combined: ~486 GB
Largest OST file: 8.7GB
Estimated emails: 1.9 million
Time to recovery: 36 hours
Required output: PST files
Why the Manual Way Was Difficult
The IT team initially considered re-creating the Outlook profiles and let the server resync the mailboxes. The approach was to bring up Exchange services first, which did not meet the immediate need to access data available locally.
They also checked the standard troubleshooting options on Microsoft. Microsoft states that Outlook can rebuild an OST when an Exchange account is available again, but that does not provide an easy way to convert an orphaned OST into a portable PST archive.
So the team needed a way to extract usable mailbox information from the OSTs that are available without waiting for the Exchange environment to be fully up and running.
The Solution
The IT admins used the TrustVare OST to PST Converter tool to handle the existing OST files and make PST copies that can be opened in Outlook.
The software supports offline, orphaned and disconnected, damaged and password-protected OST files and is capable of exporting mailbox data to PST. Supports the existing folder structure for the email, contacts, calendars, notes, tasks, journals, attachments and other components of the mailbox.
How to Convert OST to PST
1. Collect the OST files.
The administrators gathered all of the OST files available on the affected employee’s machines and transferred them to a secure recovery workstation.
2. Load OST Files
Each file was imported into the conversion application to be analyzed. The team was able to review mailbox folders and available items before exporting using the preview feature.
3. Select the mailbox data you want
Instead of exporting unnecessary folders, the administrators filtered and selected only the required mail, contacts, calendars, and other business-critical information.
4. Export PST
The selected data was migrated to PST files. In the Exchange Server recovery process, the created files can be opened or imported to Outlook.
5. Check the restored data
The IT team compared message counts, attachments, folder names, contacts and calendar information with workstation records that were available.
Results
The team was able to process all the 142 OST files that were available in the planned 36 hours recovery window. Recovered 1.9 million e-mail messages and related mailbox items to PST archives.
The IT department then passed out the PST files to priority users -- meaning that project managers, support teams and administrators could access older correspondence while the Exchange environment was rebuilt.
The recovery also provided the company with a local “cache” of critical mailbox information that could be retained for future reference.
Key Benefits
Recovery of OST file without connection: When there is no normal Exchange connectivity.
Selective export: IT administrators could choose specific folders and data.
Extraction of a large amount of mailbox components: emails, contacts, calendars, tasks, notes and journals.
Folder retention: The original mailbox folder structure could be preserved during the conversion.
Preview before export: Admins can view the available data before generating the PST files.
No source modification: The original OST data is not modified, as detailed on the official product page.
Lessons for the IT Team
The event also highlighted a key difference between server recovery and mailbox-data recovery. Restoring Exchange can get the organization’s main email environment back up and running but local cached mailbox information can also come in handy during an outage.
IT teams should also document recovery procedures, properly protect local mailbox files and avoid experimenting on original OST files. Recovery operations may be preceded by working copies. This could help avoid accidental changes.
FAQs
How to convert OST file to PST after Exchange server failure?
Yes, OST file can be converted into PST after Exchange Server crash.
Can you get OST files off of employee computers that are inoperable or orphaned?
Yes. Any usable OST files that are left on employee computers can be extracted to PST format using an OST conversion utility.
Does the OST contain a copy of the Exchange mailbox data?
An OST also includes a copy of the Exchange mailbox data. Outlook’s Cached Exchange Mode stores a copy of mailbox information in an OST file locally. The amount of data you can access is determined by your account settings and sync.
Can I retrieve only selected folders and not the entire OST?
Yes. The TrustVare tool provides options for filtering and selective data transfer for targeted recovery.
Are the Original OST Files Modified During Recovery?
Whenever possible, it is safer to keep the original files and recover them on working copies.
Conclusion
Even if employees still have valuable mailbox information on their computers, a sudden crash of the Exchange Server may prevent access to business e-mail. While the IT team fixed the main Exchange environment, they discovered a practical way to access essential mailbox data by converting accessible OST files into PST archives.
This case also illustrates why you want to plan for mailbox recovery with server-side backup and locally cached Outlook data.
