OST Recovery Benchmark & Case Study

Why benchmark OST recovery?

Recovery claims are more useful when the test conditions are visible

OST recovery results vary with source size, what Outlook previously cached, file damage, storage performance and destination workflow. A useful benchmark therefore documents the source condition, environment, recovery workflow and validation criteria instead of treating one speed or recovery percentage as universal.

Measure

The benchmark covers scan time, export time, detected folders and items, PST output size, and skipped or failed items where measured.

Validate

Open the output and check representative emails, attachments, contacts, calendar items, folder hierarchy and message properties.

Document

Source condition, EdbMails version, environment and limitations are documented so recovery results can be interpreted in context.

Evaluate your OST: Use the EdbMails OST to PST Converter to scan the source OST, preview available mailbox data, select the required folders or items, export the readable data to PST, and validate the output after export.

Test environment

EdbMails requirements and benchmark environment

The software version and system environment affect how benchmark results should be interpreted. The following values reflect the EdbMails build and published system requirements used as the baseline for this benchmark methodology.

EdbMails build

Version 6.1.2.1

Case-study OST file

testuser.ost

Case-study mailbox

testuser@edbmails.com

Supported Windows

32-bit and 64-bit Windows, including Windows 7, 8, 10, 11 and supported Windows Server editions.

Processor

Minimum 1 GHz processor. For better processing performance, EdbMails recommends at least a quad-core CPU.

Memory

Minimum 2 GB RAM. EdbMails recommends at least 4 GB RAM for better performance.

Disk and storage

Minimum 250 MB of free disk space for the application (about 225 MB installed) and its components. Additional free space is required for PST output and backup storage, depending on data size. SSD storage can improve performance with large files.

Outlook for PST export

A supported Microsoft Outlook installation with a configured profile is required for PST export. Outlook is not required to scan and preview an OST or for direct Microsoft 365/Exchange migration.

Benchmark methodology

Test multiple source sizes and source conditions

The benchmark framework covers multiple OST sizes and source conditions so accessible, orphaned, damaged and larger OST scenarios are evaluated separately.

Test	Source OST size	Condition	Purpose	Evidence
LAB-01	1 GB OST	Accessible offline OST	Baseline scan/export behavior	Scan result + PST validation
LAB-02	5 GB OST	Orphaned OST	Profile-independent recovery workflow	Preview + export report
LAB-03	10 GB OST	Damaged/corrupt OST	Evaluate readable/recoverable source data	Detected vs skipped/failed items
LAB-04	25 GB OST	Large offline/orphaned OST	Large-source processing behavior	Processing + validation record
LAB-05	50 GB OST	Orphaned OST with mixed mailbox item types	Higher-volume OST processing and validation	Environment + validation record

Source preparation: The original OST file is preserved before testing, and recovery is performed on a separate working copy. Each benchmark identifies the OST size and source condition so the results can be interpreted in the context of the tested source. Actual source filenames are retained in the test record; size-based filenames are not assigned solely for presentation.

Inventory the source

The source size, origin, known mailbox state and availability of authoritative server-side data are identified before recovery.

Preserve a working copy

The original OST remains unchanged while scanning and recovery are performed on a working copy.

Scan and preview

EdbMails scans the working copy and displays detected folders and mailbox items for preview before export.

Export or migrate

Export to PST for PST tests, or run a separate direct Microsoft 365/Exchange test when evaluating those destinations.

Validate the destination

Export results are reviewed and representative mailbox content is spot-checked in the destination.

Benchmark measurements

OST recovery benchmark results

The benchmark below records the source condition, scan duration, detected mailbox content, PST export duration and PST output size for each test. Processing time varies with OST condition, mailbox composition, storage performance, available system resources and destination I/O.

Test	OST size	Condition	Scan time	Folders	Items	Export time	PST output
LAB-01	1 GB	Accessible offline	10 min	22	8,416	30 min	1.08 GB
LAB-02	5 GB	Orphaned	55 min	31	39,782	2 hr 25 min	5.21 GB
LAB-03	10 GB	Damaged/corrupt	2 hr	38	74,913	4 hr 40 min	9.46 GB
LAB-04	25 GB	Large offline/orphaned	5 hr 15 min	54	192,648	11 hr 25 min	26.18 GB
LAB-05	50 GB	Orphaned with mixed item types	11 hr	73	381,527	22 hr 20 min	52.74 GB

Processing time can vary with OST condition, mailbox item composition, storage performance, available system resources and destination I/O. Recovery results depend on the data that remains present and readable in the source OST.

Destination validation

Measure success by more than “export completed”

A completed export is followed by data validation so the result is assessed by both job status and the usability of representative mailbox content.

Validate content

Folder hierarchy
Representative emails
Attachments present/readable in source
Contacts and calendar items
Sender, recipient, subject and timestamps

Validate the job

Successful / failed / skipped counts
PST opens in Outlook
Or target Microsoft 365 / Exchange mailbox is accessible
Representative folders and items open normally

Scan and preview evidence

The EdbMails preview is used to confirm that expected folders and representative emails, contacts, calendars and attachments are readable before export. This provides a source-side validation point before creating the PST.

Export report evidence

The export report is reviewed for successful, skipped and failed items. The resulting PST is then opened in Outlook and representative folders and mailbox items are checked against the preview.

**Figure 1. EdbMails OST scan and mailbox preview.** LAB-02 uses testuser.ost with the controlled test mailbox testuser@edbmails.com.testuser.ost; mailbox: **testuser@edbmails.com**. The preview is used to review the mailbox hierarchy and representative items before PST export.

**Figure 2. EdbMails export log.** Folder-level export activity recorded for the LAB-02 test source.

LAB profile	Folders	Items	Scan time	Export time	PST output	Failed / skipped
LAB-02	31	39,782	55 min	2 hr 25 min	5.21 GB	0

FoldersFolder-level processing recorded

ItemsExported item counts reviewed

ExceptionsExcluded or skipped folders remain visible

ValidationLog reviewed with PST spot-check

Benchmark case study

Orphaned OST recovery: from source assessment to validated PST

This benchmark case follows the LAB-02 workflow for an orphaned OST: a local OST remains available, but its original Outlook profile or mailbox relationship is no longer usable. The objective is to determine what mailbox data remains readable, preview it, export the required content to PST and validate the output.

Recovery situation

The OST is treated as a standalone recovery source. The original file is preserved and a working copy is scanned with EdbMails 6.1.2.1. Recovery is limited to data that remains present and readable in the OST.

Benchmark profileLAB-02

Source filetestuser.ost

Mailboxtestuser@edbmails.com

Source size5 GB OST

DestinationPST

EdbMails build6.1.2.1

1. Assess the available source

The workflow begins by confirming that the OST file is accessible to Windows and preserving the original file. If the authoritative Microsoft 365 or Exchange mailbox still contains the required data, the server-side source remains the preferred recovery source. The OST is used when required cached data must be assessed independently.

2. Scan and preview with EdbMails

EdbMails scans the working copy without requiring the original Outlook profile or a live Exchange connection. Detected folders and representative mailbox items are reviewed in the preview before export.

Source-first validation: Previewing the OST before export helps determine whether the required emails, contacts, calendars, attachments and folder structure are present and readable in the source file.

3. Select and export the required mailbox data

Preserve the source

The original OST remains unchanged and a separate working copy is used for scanning and recovery.

Scan and preview

Detected folders and representative mailbox items are reviewed before the export is started.

Select required data

The required mailbox folders or items are selected based on the recovery objective.

Export to PST

The selected readable data is exported to PST using a supported Microsoft Outlook installation with a configured profile.

Validate the output

The export report and resulting PST are checked for folder structure, representative items, attachments and mailbox properties.

4. Validation outcome

Validation point	Benchmark check	Evidence
Source processed	LAB-02, 5 GB orphaned OST profile	Source inventory
Folder visibility	Detected folders reviewed in preview	EdbMails scan and preview
Mailbox content	Representative emails, contacts, calendars and attachments reviewed	Preview + PST spot-check
Export exceptions	Successful, skipped and failed statuses reviewed after export	Export report
PST usability	Resulting PST opened and representative content checked	Outlook validation
Recovery scope	Limited to data present and readable in the source OST	Source condition + validation

Interpret the results correctly

What this benchmark cannot guarantee

These limitations define how the benchmark should be interpreted and why results from one OST cannot be treated as a universal recovery guarantee.

An OST may not contain the full server mailbox

Cached Exchange Mode settings, synchronization history, shared-folder caching and mailbox state determine what exists locally. Microsoft Online Archive is separate server-side content and should not be assumed to exist in the primary OST.

Damaged sources can produce different results

Recoverability depends on which structures remain readable. One damaged OST cannot predict the result for another file with different corruption or overwritten data.

Speed is environment-dependent

CPU, memory, storage, source condition, security software and destination I/O can materially change scan and export duration.

External encryption must be handled first

EdbMails does not bypass BitLocker, Windows EFS, ransomware encryption, passwords or other external access controls. The OST must be accessible to Windows before it can be analyzed.

Benchmark interpretation: The benchmark framework describes specific source conditions and validation checks. It does not guarantee identical speed, item counts or recoverability for another OST.

Reproducibility

How the OST Recovery Benchmark Is Performed

The original OST is preserved and a separate working copy is used for the benchmark.
The EdbMails version, supported Windows environment, system resources and applicable Outlook configuration are identified.
The OST is scanned and detected folders and mailbox items are reviewed in the preview.
For PST testing, selected readable data is exported and the resulting PST is retained for validation.
The export report is reviewed for successful, skipped and failed items.
The PST is opened in Outlook and representative emails, attachments, contacts, calendars, folder hierarchy and message properties are checked.
The source condition and environment are considered when interpreting performance and recoverability.

The same validation categories are used across the benchmark profiles so accessible, orphaned, damaged and larger OST sources can be assessed consistently.

Frequently asked questions

OST benchmark and recovery questions

Does a successful OST scan prove that the OST contains the complete mailbox?

No. An OST is a synchronized local cache and may not contain every server-side item. Cache settings, synchronization history, shared-folder caching and Online Archive can affect what exists locally.

Is Outlook required to scan an OST with EdbMails?

Outlook is not required to scan and preview the OST. A supported Outlook installation with a configured profile is required when exporting recovered OST data to PST. Outlook is not required for direct migration to Microsoft 365 or Exchange.

Are benchmark results a recovery guarantee?

No. They are measurements from documented test files and a documented test environment. Another OST may differ in source data, damage, storage performance and recoverability.

Why test orphaned and damaged OST files separately?

Orphaning and physical/logical file damage are different conditions. An orphaned OST may be readable but no longer usable through its original mailbox/profile relationship, while a damaged OST may contain unreadable structures.

Should I recover an old OST if the live Microsoft 365 or Exchange mailbox is healthy?

Usually not. If the authoritative server mailbox contains the required data, reconnect or recreate the Outlook profile and let Outlook build a fresh OST. Recover the old OST when it contains required data unavailable from the authoritative source.

Related resources

Continue with the appropriate OST workflow

Evaluate your own OST before purchasing

Use EdbMails to scan and preview the source, then verify representative mailbox data before choosing the recovery or migration path. The free trial currently allows export of up to 30 items from each folder.

View OST to PST Converter Try the Free Version

Just $129 Onwards

OST Recovery Benchmark & Case Study

Recovery claims are more useful when the test conditions are visible

Measure

Validate

Document

EdbMails requirements and benchmark environment

EdbMails build

Case-study OST file

Case-study mailbox

Supported Windows

Processor

Memory

Disk and storage

Outlook for PST export

Test multiple source sizes and source conditions

Inventory the source

Preserve a working copy

Scan and preview

Export or migrate

Validate the destination

OST recovery benchmark results

Measure success by more than “export completed”

Validate content

Validate the job

Scan and preview evidence

Export report evidence

Orphaned OST recovery: from source assessment to validated PST

Recovery situation

1. Assess the available source

2. Scan and preview with EdbMails

3. Select and export the required mailbox data

Preserve the source

Scan and preview

Select required data

Export to PST

Validate the output

4. Validation outcome

What this benchmark cannot guarantee

An OST may not contain the full server mailbox

Damaged sources can produce different results

Speed is environment-dependent

External encryption must be handled first

How the OST Recovery Benchmark Is Performed

OST benchmark and recovery questions

Continue with the appropriate OST workflow

Evaluate your own OST before purchasing