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on December 30, 2025
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Therefore, now we will know the steps to repair the Outlook data file. Here, we will discuss the five manual methods to fix sync issues in Outlook or OWA. Before finding solutions, we suggest that users check their internet connection. Sometimes, Outlook sync issues can arise because of poor internet connection. If you are still facing this issue, kindly follow the solutions below to fix the sync issues in Outlook.
Methods to fix Microsoft Outlook syncing error
It scans your local copy of the .ost file and your mailbox on an Exchange Server. The tool compares items and folders in the file and in your mailbox and tries to reconcile synchronization differences between the files and the mailbox. The OST Integrity Check Tool does not change your mailbox on the Exchange Server.
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The tool does not interact with your mailbox on the Exchange Server.Outlook and Office 365 sync issues can be frustrating but are almost always fixable.The OST Integrity Check Tool does not change your mailbox on the Exchange Server.Outlook lets you manually control which folders sync with the server.The scan log also identifies any situations that the tool could not resolve and that you must fix manually.Any problems are noted in a message that has "OST Integrity Check" as its Subject.FixTechGuide continues to help users resolve Outlook and Office 365 errors quickly and safely.
Users can also try its free demo version in their system and process the first 50 items from each folder freely. Outlook and Office 365 sync issues can be frustrating but are almost always fixable. Start with basic network checks, enable Cached Exchange Mode, and repair your data files if needed. For persistent problems, rebuild your Outlook profile or use FixTechGuide’s free diagnostic tools to automate detection of authentication and IMAP errors in seconds. The OST Integrity Check Tool runs only on .ost files and can be used to diagnose and repair synchronization issues.
Step 4: Repair the Outlook OST File
If you have a slow internet connection or large mailboxes, default timeouts may be too short. Faulty add-ins (especially antivirus or CRM extensions) can freeze Outlook during synchronization. For a similar error caused by rebuild Outlook data file quickly a different issue, refer to Outlook shows Disconnected in status bar if the last character in legacyExchangeDN is a space. This mode is ideal for slow connections or intermittent server responses. If Outlook syncs fine now, re-enable add-ins one by one to find the culprit.
Step 10 – Rebuild Offline Cache (OST)
If this method doesn’t work for you, navigate to other solutions. resolve Outlook not sending emails fast Before you dive into folder sync issues, read our complete Outlook and Office 365 Sync Guide for an overview of how synchronization works. By limiting synchronization to active folders, Outlook finishes updates faster and avoids timeouts. Use the OST Integrity Check Tool (Scanost.exe) to check your .ost file for inconsistencies. When these symptoms occur, or you have other problems synchronizing, the problem might be a corrupted .ost file. Users can also convert OST files into various file formats, including PST, HTML, EML, MSG, vCard, etc.
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When synchronization issues occur in Microsoft Outlook or in Microsoft Outlook Web App (formerly Outlook Web Access), you may experience the following symptoms. Knowing the reasons behind the Outlook sync issues will help us to fix this problem and prevent Outlook data file cannot be accessed issues in communication and workflow. There can be several reasons for the Outlook synchronization error.