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5 Ways to Rebuild an OST File in Outlook (2019, 2016, 2013, 2010)

Outlook stores a local, offline copy of your mailbox — emails, contacts, calendar entries, and attachments — in an OST (Offline Storage Table) file. This lets you keep working even without an internet connection; any changes you make sync back to the server once you're reconnected. Outlook creates this file automatically when your account is set up with Exchange, Office 365, or an IMAP server.

When the OST file becomes damaged or unreadable, Outlook can start throwing sync errors, freezing, or failing to open the mailbox altogether. Rebuilding the file is the standard fix, but it comes with a catch: rebuilding only restores what's already on the mail server. Anything that existed only in the local OST and hadn't synced yet is gone for good unless you recover it first.

This guide covers what typically causes OST corruption, five ways to rebuild or repair the file in Outlook 2019, 2016, 2013, and 2010 — from lightest-touch to most thorough — and how to recover data from a damaged OST file before rebuilding, using EdbMails OST to PST Converter, so you don't lose anything in the process.

Rebuild Outlook OST file

Common Causes of OST File Corruption

A few conditions account for most OST corruption and access issues:

Oversized OST file — once an OST file grows very large, Outlook can struggle to manage it, leading to slowdowns, instability, or corruption. Splitting the file into multiple PST files is a common fix.
Virus or malware infection — malware can alter the OST file's internal structure, making it unreadable and breaking synchronization.
Sudden power failure or forced shutdown — if the system shuts down while Outlook is syncing the OST file, the file can be left in a corrupted state.
Network connectivity issues — an unstable or interrupted connection to the Exchange server during synchronization can corrupt the file.
Storage device issues — bad sectors or hardware faults on the drive where the OST file is stored can damage it.
Outlook software issues — outdated Outlook builds, software bugs, or incompatible/faulty add-ins can also trigger OST corruption or sync failures.

How to recreate OST file in Microsoft Outlook 2019, 2016, 2013, 2013, and 2010?
- Although recreating the OST file can fix corruption issues, it often leads to missing emails and data loss—especially if recent changes weren't synced with the server. To avoid this, rebuilding the OST file requires a careful, step-by-step approach.
  Method 1: Repair with Outlook's Inbox Repair Tool (ScanPST.exe)
  Before rebuilding the file from scratch, it's worth trying Outlook's own built-in repair utility first — it can fix minor corruption without touching your data.
  - Step 1: Close Outlook
    Make sure Outlook and all related mail apps are fully closed.
  - Step 2: Locate ScanPST.exe
    Open File Explorer and go to your Office installation folder:
    C:\Program Files (x86)\Microsoft Office\root\OfficeXX (replace 'XX' with your Office version, e.g. Office16 for Office 2016/2019/365).
  - Step 3: Run the scan
    Double-click scanpst.exe, click 'Browse' and select your OST file, then click 'Start'.
  - Step 4: Repair any errors found
    If the tool finds errors, click 'Repair' to fix them, then reopen Outlook to confirm the issue is resolved.
  Limitations of ScanPST
  ScanPST is designed for minor corruption only and may not fix severe damage. It also carries a data-loss risk of its own — back up the OST file before running it — and can be slow on oversized files. If ScanPST can't resolve the issue, move on to one of the rebuild methods below.
- Method 2: Rebuild an OST File by Enabling Cached Exchange Mode
  Cached Exchange Mode keeps an offline copy of your Exchange mailbox on your computer as an OST file. Re-enabling it forces Outlook to generate a new one.
  - Step 1: Open Microsoft Outlook and go to the File menu
    Click 'File' in the top-left corner of the Outlook window.
  - Step 2: Open Account Settings
    From the drop-down, select 'Account Settings' and then 'Account Settings' again.
  - Step 3: Enable Cached Exchange Mode for your account
    Select the email account you want to rebuild the OST file for, then click 'Change'.
    In the Change Account window, check 'Use Cached Exchange Mode' and click 'Next'.
    Click 'Finish' to complete the change.
  - Step 4: Close and relaunch Outlook
    Outlook automatically creates a new OST file for the account you selected in Step 3.
- Method 3: Rebuild an OST File by Renaming or Deleting It
  You can also force Outlook to rebuild the OST file by renaming or moving the existing one. Back up the file first — this method deletes any unsynced local data.
  Step 1: Close Microsoft Outlook
  - Make sure Outlook isn't running in the background.
  Step 2: Locate the existing OST file
  - Default location: C:\Users\%username%\AppData\Local\Microsoft\Outlook\
  - Or navigate to File > Info > Account Settings > Account Settings > Data Files > Open File Location.
  Step 3: Rename the OST file
  - Change the file extension — for example, rename Outlook.ost to Outlook.old.
  Step 4: Relaunch Outlook
  - Outlook creates a new OST file and begins synchronizing with the Exchange server automatically.
  For step-by-step instructions specific to older Outlook builds, see how to create or rebuild an Outlook OST file.
  Limitation
  Renaming or deleting the OST file to rebuild it only restores data that still exists on the mail server. Any emails or items that were only stored locally and never synced — for example, drafts or recently received mail during an outage — cannot be recovered this way. To restore that data, you need to convert the original OST file to PST before it's overwritten.
- Method 4: Rebuild an OST File by Creating a New Outlook Profile
  If renaming the OST file doesn't resolve the issue, the underlying problem may be a corrupted Outlook profile rather than the OST file itself. Creating a fresh profile rebuilds the OST file as part of setting up the new profile.
  Step 1: Open the Mail settings in Control Panel
  - Open Control Panel, then go to Mail (Microsoft Outlook).
  Step 2: Open profile management
  - Click 'Show Profiles,' then 'Add' to create a new profile.
  Step 3: Configure the new profile
  - Enter a name for the profile and configure your email account details.
  Step 4: Set it as default and restart Outlook
  - Select 'Always use this profile,' then restart Outlook — a new OST file is generated automatically under the new profile.
- Method 5: Recover and Rebuild an OST File with EdbMails OST to PST Converter
  If you need to recover data before rebuilding — or the OST file is too damaged for Outlook or ScanPST to handle — EdbMails OST to PST Converter can recover the file independently of Outlook or the Exchange server, then convert it to a PST file you can import back into Outlook. It supports OST files from Outlook 2019, 2016, 2013, and 2010.
  1. Download and install EdbMails on any Windows-based computer — no Exchange server connection is required.
  2. Log in or start a free trial, then select 'OST Recovery and Migration' > 'OST to PST'.
  3. Browse to and select the corrupted or inaccessible OST file.
  4. Preview the recovered mailbox contents and select the folders or items to export.
  5. Choose a destination and export the data to PST format.
  6. Import the resulting PST file into Outlook to restore your mailbox data.

Why Use EdbMails to Rebuild a Corrupted OST File

Automated Mailbox Recovery — recovers corrupted OST files and restores mail items from a backup snapshot of the OST automatically.
Easy-to-Use Interface — a straightforward, guided workflow that doesn't require technical expertise.
Efficient Scanning — advanced scanning algorithms perform granular recovery of every mail item, not just a bulk restore.
Customizable Recovery — selective recovery of emails, contacts, and calendars using include/exclude filters.
Fast and Secure — recovers data quickly while preserving formatting and data integrity throughout export and migration.
No File Size Limitations — recovers OST files of any size, and can split an oversized file into multiple smaller PST files.
Multiple Export Options — export to PST, HTML, EML, or MHT, or migrate directly to Office 365 or Live Exchange.

Frequently Asked Questions

What is the default OST file location in Outlook 2010, 2013, 2016, and 2019?
The OST file is stored at C:\Users\%username%\AppData\Local\Microsoft\Outlook\ across these versions. You can also find it via File > Info > Account Settings > Account Settings > Data Files > Open File Location.
How do I create an OST file in Outlook 365?
An OST file is created automatically the first time Outlook connects to a Microsoft Exchange account. To recreate one manually: open Outlook 365, go to File > Account Settings > Account Settings, click the Data Files tab, select 'Open File Location,' note the file's location, close Outlook, rename the OST file, then relaunch Outlook to rebuild it. You may need Cached Exchange Mode enabled for Outlook to generate the file.
How do I rebuild the OST file if I can't access Outlook?
You can still rename the OST file directly from File Explorer and relaunch Outlook to force it to rebuild a new one. If you need to preserve the data in the old file rather than starting fresh, use EdbMails OST to PST Converter to recover it and convert it to PST first.
Can a corrupted OST file be repaired?
Yes. Microsoft Outlook includes a built-in repair tool, Scanpst.exe (Inbox Repair Tool), that can fix minor OST issues. For more severe corruption, third-party tools like EdbMails OST to PST Converter can recover and repair the file, including OST files that are encrypted, password-protected, or otherwise inaccessible.