Step-by-Step Guide to Recreate OST Files for Outlook 2016–2003
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- February 23rd, 2026
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Outlook stores mailbox data for Exchange and some IMAP accounts in an Offline Storage Table (.ost). When synchronization problems, corruption, or profile errors occur, it is often necessary to recreate OST files to restore normal operation. This article explains how to safely recreate OST files in Outlook 2016, 2013, 2010, 2007, and 2003 and covers steps, file locations, and alternatives.
- Recreate OST files by closing Outlook, renaming or deleting the OST, and restarting Outlook to resynchronize from the mailbox server.
- For Exchange/Office 365 and IMAP accounts this is normally safe; for accounts that store data only in OST, export or back up before deleting.
- If the OST cannot be rebuilt, consider creating a new profile, using built-in Outlook command switches, or exporting to PST with a supported tool.
Understanding OST files and when to recreate OST files
An OST file is a cached copy of mailbox data used primarily by Exchange and some IMAP accounts when Cached Exchange Mode is enabled. Recreate OST files when Outlook shows errors such as synchronization failures, broken search index, frequently prompted credentials, or when the OST is reported as corrupted. For authoritative guidance on supported procedures and account types, consult Microsoft Support and Exchange documentation.
Prepare before rebuilding an OST
Confirm account type
Verify whether the account is Exchange, Exchange Online (Office 365), IMAP, or POP. For Exchange and IMAP, the server keeps the master copy of emails, so an OST can usually be safely recreated. For POP profiles or orphaned OST data (no server copy), export or backup important items before deleting the OST.
Back up important data
Before deleting or renaming an OST, export mail, contacts, calendars, and tasks to a PST file if any data exists only locally. Use Outlook's Export feature or an administrator-approved backup; do not assume every item exists on the server.
General steps to recreate OST files in Outlook
1. Close Outlook and related processes
Exit Outlook. Confirm no Outlook.exe processes remain using Task Manager (Windows) or equivalent.
2. Locate the OST file
Default OST locations by Outlook version (Windows):
- Outlook 2013, 2016, 2019, and Microsoft 365: %LOCALAPPDATA%\Microsoft\Outlook
- Outlook 2010: %LOCALAPPDATA%\Microsoft\Outlook
- Outlook 2007: %USERPROFILE%\AppData\Local\Microsoft\Outlook or on Windows XP: %USERPROFILE%\Local Settings\Application Data\Microsoft\Outlook
3. Rename or delete the OST file
Rename the .ost file to .ost.old or move it to a backup folder. Renaming is safer because it preserves the original if it is needed later. Deleting also forces Outlook to create a new OST when synchronization occurs.
4. Restart Outlook to rebuild
Launch Outlook. The application will detect the missing OST and create a new one, then synchronize mailbox folders and items from the server. Depending on mailbox size and network speed, resynchronization can take from minutes to hours.
Outlook-specific and advanced methods
Create a new Outlook profile
When problems persist, creating a new mail profile forces a clean OST creation. In Control Panel > Mail > Show Profiles > Add, create a new profile, configure the account, and set it as default. This is especially useful for profiles with corrupted settings.
Use Outlook command switches
Outlook includes switches that can help fix view or folder problems before recreating the OST. Useful switches include:
- /resetfolders — restores missing default folders
- /resetnavpane — resets the navigation pane and startup options
Repair and index considerations
For search issues, rebuilding the Windows Search index or resetting Outlook search may help. The Inbox Repair Tool (scanpst.exe) works with PST files, not OSTs. Microsoft recommends using profile recreation or OST deletion for OST issues.
When a direct rebuild is not possible
OST contains unique local-only data
If the OST holds items that are not on the server (rare for properly configured Exchange/IMAP), export those items to PST before removing the OST. If Outlook cannot open the OST, third-party conversion utilities can extract mailbox items, but choose software vetted by IT policies and verify with the organization’s administrator.
Contacting support and compliance
For enterprise environments or when mailbox retention and compliance rules apply, consult Exchange administrators or Microsoft documentation before deleting profile data. Official Microsoft Support articles explain differences between OST and PST and server-side synchronization behavior. For additional manufacturer guidance see the Microsoft Support site: support.microsoft.com.
Troubleshooting checklist
- Ensure network connectivity and server availability before attempting a rebuild.
- Verify mailbox size—large mailboxes take longer to resynchronize.
- Check disk space where the OST will be created.
- Review Exchange/IMAP server policies that may limit synchronization or cached item ranges.
- If problems persist, create a new Outlook profile or escalate to the IT administrator.
Best practices
- Keep regular backups of PST exports if local-only items are used.
- Prefer Cached Exchange Mode for better offline performance, but monitor OST size.
- Document any changes to profiles and OST locations for future troubleshooting.
FAQ
How to recreate OST files in Outlook 2016/2013/2010/2007/2003?
Close Outlook, locate and rename or delete the .ost file (default under %LOCALAPPDATA%\Microsoft\Outlook for modern versions), then restart Outlook. The client will create a new OST and resynchronize with the server. Back up local-only data first and consider creating a new profile if problems continue.
Will deleting an OST cause data loss?
For Exchange and IMAP accounts, deleting an OST should not cause data loss because the server keeps the master copy. If items exist only locally, exporting to a PST before deletion is essential. Always back up important data before making changes.
Can scanpst.exe fix an OST?
No. scanpst.exe is designed to repair PST files. For OST issues, recreate the OST by removing or renaming it or recreate the mail profile. If recovery of local-only data from a damaged OST is required, consider approved third-party extraction tools and consult administrators.
How long does rebuilding an OST take?
Rebuild time depends on mailbox size, server speed, and network bandwidth. Small mailboxes may resync in minutes; large mailboxes can take hours. Monitor synchronization progress in Outlook’s status bar.
