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    OST to PST Converter

    How to Resolve Sync Issues in Outlook – A Detailed Guide

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      Summary: Sync Issues folder and messages in its subfolders can’t be ignored as they can quickly fill up your mailbox and lead to mailbox full error if the causes behind the sync issues are not fixed. In this post, we have discussed the Sync Issues folder, shared the reasons behind the Sync Issues, and how to safely resolve them and avoid exceeding your mailbox quota.

      The Sync Issues folder is a special mail folder in MS Outlook that stores messages containing information on synchronization issues and error logs experienced by the client. These messages are sent by the mailbox server, such as Microsoft Exchange, to inform users about the problems encountered while synchronizing the emails or other mail items in Outlook to or from the mailbox server.

      By default, Sync Issues folder and its subfolders are not visible in Outlook. To view the folder and its subfolders, click the three dots at the bottom navigation pane and choose ‘Folders.’

      view sync issues folder

      It contains three subfolders, which are as follows:

      • Local Failures

      This Sync Issues subfolder stores information on mail items that could not be sent to the mailbox server from the local Outlook data file.

      • Conflicts

      This Sync Issues subfolder stores multiple copies of conflicting mail items in the mailbox that can significantly inflate the mailbox size as Outlook tries to sync the mail items again and again. 

      • Server Failures

      This Sync Issues subfolder stores mail items that Outlook could not synchronize with the mailbox server.

      click on sync issues folder in outlook

      If you open the email in Sync Issues or any of its subfolders, you may come across error messages, such as:

      08:18:17 Synchronizer Version 15.0.5267
      08:18:17 Synchronizing Mailbox 'Ravi Singh'
      08:18:17 Synchronizing Hierarchy
      08:18:17 Synchronizing server changes in folder “Folder Name’
      08:18:17 Downloading from server ‘’
      08:18:17 Syncmonitor triggered for ;Folder Name’ (0x80004005)
      08:18:17 Error synchronizing folder
      08:18:17          [80004005-501-4B9-560]
      08:18:17          The client operation failed.
      08:18:17          Microsoft Exchange Information Store
      08:18:17          For more information on this failure, click the
      URL below:
      08:18:17 Done
      08:18:17 Microsoft Exchange offline address book
      08:18:17 Download successful 
      sync issues error messages

      Reasons for Sync Issues

      Sync issues in the Outlook client may occur due to one or more of the following reasons:

      • Oversized or large OST file
      • Faulty or incompatible Add-ins
      • Network connection/firewall issues
      • Corrupt or damaged Outlook profile
      • Hardware or software issues

      Further, it may also occur when,

      • The email or mail items deleted or changed no longer exist in your mailbox or the item was already deleted from the mailbox.
      • The Exchange Server cannot delete or perform the requested changes to the item.

      Solutions to Fix Sync Issues in Outlook

      Although the Sync Issues folder can be safely ignored in most cases, it can quickly increase the mailbox size and fill up the default Outlook mailbox quota in some cases which can lead to send/receive errors, new synchronization errors, and failed message deliveries.

      When the mailbox is full, the synchronization stops between the Outlook client and mailbox server, leading to further problems, such as:

      • Failure in sending or receiving new emails
      • Outdated mailbox or mismatch in the number of emails between Outlook and Outlook Webmail (OWA).
      • Error codes, such as “Mailbox size exceeds error 0x8404060c” while manually syncing the mail items in Outlook.

      Thus, fixing the Sync Issues is critical. Follow these solutions to fix the problem.

      Note: It’s critical to read the messages received in the Sync Issues folder to specifically address the problem and permanently fix it to further issues.

      Check Network Connection

      Synchronization requires an active network connection with the mailbox server. An unreliable and poor network connection or firewall settings can obstruct Outlook from synchronizing the mail items stored in the IMAP OST file to the mailbox server. Similarly, if the mailbox server is down, it can prevent Outlook from synchronizing the mail items.

      To troubleshoot the issue, try reconnecting the network cable or WLAN. Then check the internet connection and firewall settings. You may also contact your IT support to ensure a network firewall isn’t blocking the mail server. Also, log in to your email account using a web browser to ensure your account is active and the server is available.

      Repair OST File

      You can use the OST integrity check tool (SCANOST.exe) in Outlook 2003 and 2007 or the Inbox Repair tool (ScanPST.exe) in Outlook 2010 and later versions to try fixing the errors or repair the corrupted OST file. This may help resolve the Sync Issues problem in your Outlook client.

      The steps are as follows:

      In Outlook 2003 or 2007

      • Run the ScanOST.exe.
      • Select the profile name where you are experiencing the issues from the list and click Connect (if prompted).
      • Select the desired option and let the tool find the issues.
      • Click the Repair Errors checkbox.
      • Click begin Scan.

      In Outlook 2010 and later versions

      • Launch the ScanPST.exe tool. Refer to our article on how to find ScanPST location.
      • Click Browse and select the OST file associated with your email profile.
      • Click Start.
      • After the scan, click Repair.
      • The tool will try to fix the inconsistencies and errors found in the OST file. Once finished, start Outlook.

      This may fix the Sync Issues in your Outlook if caused by an inconsistent OST file. 

      Setup a New Outlook Profile

      By setting up your email account under a new Outlook profile, you can replace the corrupt one and may fix the Outlook Sync Issues.

      The steps to set up a new profile in Outlook are as follows:

      • Open Control Panel, search and click on Mail.
      show outlook profiles
      • Click Show Profiles > Add.
      add new outlook profile
      • Enter your new profile name (type any name) and click OK.
      name new outlook profile
      • Configure your IMAP, Exchange, or Office 365 email account, and then click Next > Finish.
      configure your email account under the new outlook profile
      • Select ‘Always use this profile’ and then choose the newly set up Outlook profile from the dropdown.
      choose new profile as default
      • Click OK and then restart Outlook.

      Change the Root Folder Path

      When Outlook fails to detect the default root folder path, it may lead to sync issues in Outlook. However, you can manually set the root folder path by following these steps and resolving the problem.

      • In Outlook, navigate to File > Account Settings > Account Settings and double-click on your email account.
      • Click More Options… > Advanced.
      • Check if the root folder path is set to Inbox. If not, choose Inbox and click Save.
      • Exit and restart Outlook.
      • After restarting, go to the Send/Receive tab and click Update Folder.
      • This will start the synchronization. Wait for it to finish and then check if there’re new messages in the Sync Issues folder.

      Resync the Mail Folders

      If the messages in the Sync Issues folder indicate a problem with a specific folder, you can try to resync the folder in Outlook by following these steps:

      • Right-click on the folder and choose Properties.
      • Click Clear Offline Items > OK.
      • After clearing the offline items, click the Update Folder option under the Send/Receive tab.

      Rebuild Outlook Data File (OST)

      If the sync issues are caused by faulty OST file, you can fix the problem by recreating or rebuilding the OST file.

      The steps are as follows:

      • In Outlook, navigate to File > Account Settings > Account Settings and click on the Data File tab.
      • Choose the email account and click ‘Open file location….’ Alternatively, you can right-click on your email profile in Outlook (left pane) and choose Open File Location to open the folder location where the default OST is stored.
      • Close Outlook and copy the default OST file to a safe location for backup.
      • After the backup, delete the OST
      • Start Outlook. This will recreate a new OST file.

      After rebuilding the new OST file, Outlook will start synchronizing the mail items. This should fix the Outlook Sync Issues.


      By following the solutions discussed in this guide, you can fix the Sync Issues and avoid messages in the Sync Issues folder from filling up your mailbox and leading to a mailbox full or a synchronization error. When nothing works to fix the problem, you can switch to the online mode or recreate the OST file.

      After the OST file is recreated and synchronization is finished, you will see ‘All folders are up to date in the Outlook status bar. Make sure to check all mail folders to ensure all mail items are synchronized from the server. However, if you don’t find your recent or newer mail items after synchronization is finished, you can use an OST to PST converter tool, such as Stellar Converter for OST to convert the backup OST file into PST format and import the converted PST file into your Outlook to restore the missing mail items. Besides, the software can also extract mail items from an orphaned, inaccessible, or encrypted Outlook OST file and directly export the items to an existing Outlook profile, Office 365, or live Exchange mailbox with complete integrity.  


      You can manually sync Outlook emails via Send/Receive > Update Folders in Outlook.

      Yes, it’s completely safe to delete the Sync Issues folder. However, deleting the folder won’t resolve the problem and the folder will appear again with new messages.

      The Sync Issues folder is hidden by default. You can click on the three dots at the bottom of the left pane and click the Folders option to view the Sync Issues folder..

      You can try to fix slow Outlook IMAP folder synchronization issues by going to File > Info > Account Settings > Account Settings > More Options > Advanced Settings and ensuring that the Root folder path says Inbox.

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      About The Author

      Ravi Singh linkdin

      Ravi Singh is a Senior Writer at Stellar®. He is an expert Tech Explainer, IoT enthusiast, and a passionate nerd with over 7 years of experience in technical writing. He writes about Microsoft Exchange, Microsoft 365, Email Migration, Linux, Windows, Mac, DIY Tech, and Smart Home. Ravi spends most of his weekends working with IoT (DIY Smart Home) devices and playing Overwatch. He is also a solo traveler who loves hiking and exploring new trails.

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