Updated 17 September 2026
How to verify an MBOX-to-PST conversion
Open the converted PST in classic Outlook, then compare its folders, message counts, sample messages, and attachments with the MBOX source. A PST that opens can still have missing or repeated mail.
Record the test before conversion
Before you start, make a simple note of the source mail program, the MBOX files and folders you selected, their sizes, your converter version and settings, and where the PST will be saved. Keep the original MBOX folder unchanged. If the source mail program shows a folder list and message counts, save those too. For an important archive, a file hash—a calculated digital fingerprint—can help you confirm later that a source file did not change.
Check the PST opens cleanly
Open the PST as a separate data file in classic Outlook. Confirm that it appears in the folder pane, expand each main folder, and open a few messages. Close and restart Outlook once, then make sure the PST still opens. This confirms that Outlook can read and navigate the file; the remaining checks show whether its contents match the source.
Compare the folder structure
Swipe or scroll to compare all columns.
| What to check | What to compare | Why a difference may appear |
|---|---|---|
| Main folders | Source folder list against the PST list | The wrong source folder or PST destination was selected |
| Nested folders | Number of levels, names, and a few folders at each level | A companion .sbd folder was not copied, or subfolder processing was turned off |
| Special folders | Inbox, Sent, Archive, and Junk | Mail programs use different names and rules for these folders |
| Gmail labels | The chosen folder or category result, especially for messages with several labels | One Gmail message can have more than one label |
Check a varied set of messages
Open a varied group of messages rather than only the first few in the Inbox. Include some of the oldest and newest mail, messages from nested folders, a large message, and text with accents or non-Latin characters. Check plain-text and formatted HTML mail, several attachment types, pictures displayed inside a message, long subject lines, dates from different time zones, and the message details you need to retain. If you enabled Add Internet headers, compare the full headers of a few source and converted messages. Open each sampled attachment and check its contents, not only its filename.
Compare message counts
Compare the message count in each source folder with the matching PST folder whenever both programs show a count. Write down any known reason for a difference, such as a filter you selected, a skipped or damaged MBOX file, repeated messages, or one Gmail message copied for several labels. Matching grand totals are useful, but they can hide one missing folder and another duplicated folder, so check the folder list as well.
Review duplicates, errors, and retries
Keep the conversion log and look for messages or files reported as skipped, damaged, or failed. Before running the converter again, note which MBOX files finished successfully. Moving completed source files to another folder can stop those files from being processed again, but it cannot remove duplicate messages already present in two exports. If you are unsure what a retry will do, send it to a new test PST first.
Save your results
When the checks are complete, save a short record of the source and PST locations, converter version, settings, date, folders and sample messages checked, and any differences you could not explain. Keep the original MBOX until the verified PST has a separate backup. For workplace mail, follow your organization's retention and deletion rules.
Primary sources
- Microsoft: Open and close Outlook Data Files
- Microsoft: Repair Outlook Data Files with SCANPST
- ReliefJet: Convert MBOX to PST
FAQ
Is opening the PST enough to check the conversion?
No. Also compare the folders and message counts with your original mailbox, open old and recent emails, and try several attachments. Check the conversion log for anything skipped.
Which emails should I check?
Choose old and recent emails from several folders. Include messages with attachments, embedded images and names in different languages, as well as any messages that matter especially to you.
When can I delete the original MBOX files?
Keep them until you have checked the converted email and saved a separate backup. For work email, follow your organization’s rules on how long messages must be kept.
Something missing from the PST?
Review the conversion settings before trying again. Save the next result to a new PST so you can compare the two.