How to Rebuild an OST File in Outlook (2007, 2010, 2013, 2016)

March 27, 2026

If your Outlook is not syncing properly or showing errors, rebuilding the OST file can often solve the issue. This method works for Outlook 2007, 2010, 2013, and 2016.

In this guide, you will learn how to safely rebuild your OST file step by step.

Video Tutorial

What Is an OST File

An OST file (Offline Storage Table) stores a local copy of your mailbox data when using Exchange accounts. If this file becomes corrupted or outdated, Outlook may stop syncing correctly.

When You Should Rebuild the OST File

You may need to rebuild the OST file if:

Emails are not syncing
Outlook is slow or freezing
You see send/receive errors
Missing emails or folders
OST file is corrupted

Step 1: Close Outlook

Make sure Outlook is completely closed before making any changes.

Step 2: Locate the OST File

The OST file is usually located here:

%localappdata%\Microsoft\Outlook

Steps:

Press Windows + R
Paste the path above
Press Enter

Step 3: Rename or Delete the OST File

To rebuild the OST file:

Find your OST file
Right-click and rename it (for example: backup.ost)
or delete it
Close the folder

Renaming is safer because you keep a backup.

Step 4: Reopen Outlook

Start Outlook again.

Outlook will automatically create a new OST file and begin syncing your mailbox from the server.

Important Notes

This method only works if your data exists on the server (Exchange, IMAP)
If the OST file contains unsynced data, it may be lost
Always rename instead of deleting if you are unsure

When This Method Does Not Work

If Outlook cannot rebuild the OST file or you need to recover data from it, you may need a recovery tool.

A tool like Stellar Converter for OST can help you:

Convert OST to PST or EML
Recover inaccessible emails
Export data for reuse

Final Notes

Rebuilding the OST file is one of the most effective ways to fix Outlook sync and performance issues. In most cases, this simple process restores Outlook to normal.