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Emails not updating when using outlook cached mode

Anonymous
2025-06-12T16:36:37+00:00

We are using an Office 365 account with an E3 license, connected to the latest version of Outlook (desktop app). When operating in Cached Exchange Mode, emails do not update automatically. All pending emails are only received after restarting Outlook.

However, email works correctly in Online Mode, with no delays in mail delivery.

Please assist to resolve this issue..

Outlook | Windows | Classic Outlook for Windows | For home

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  1. Anonymous
    2025-06-12T23:30:53+00:00

    Dear U_Nuwan,  

    Thank you for your update, and I truly appreciate the time and effort you've invested in working through the recommended steps. 

    Since the problem is isolated to one mailbox and continues to persist, we may be dealing with a deeper issue that warrants further investigation. 

    I'd suggest trying the following steps:   

    1. Test the Affected Mailbox on Another Device If possible, configure the same mailbox on a different Windows device using the New Outlook. This can help determine whether the issue is tied to the mailbox itself or the local environment.
    2. Check for Hidden Corruption or Sync Conflicts
    • In Outlook, go to File > Info > Account Settings > Account Settings > Data Files.
    • Select the affected mailbox and click Open File Location.
    • Right-click the OST file > Properties > General tab > check for abnormal file size or frequent modification timestamps.
    • You can also enable the Sync Issues folder (via Folder List view) to check for any logged errors.
    1. Run Microsoft Support and Recovery Assistant (SaRA)
    1. Escalate to Microsoft 365 Admin Support As Microsoft Community Moderators, we have limited access to tenant-level diagnostics and configuration tools. Since this issue appears to be isolated to a single mailbox and persists despite multiple remediation steps, we recommend escalating it through your Microsoft 365 Admin Center by submitting a support ticket. This will allow our engineering team to review mailbox-level logs and sync telemetry to identify any potential service-side or backend-related causes.

    Please let us know if you’ve already submitted a support request sharing the case ID will help us coordinate more effectively. We're committed to helping you get this resolved. 

    Warm Regards,    
    Chris-DKN - MSFT | Microsoft Community Support Specialist.

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  1. Anonymous
    2025-06-12T17:38:31+00:00

    Hi Chris,

    Thank you very much for your response.

    We’ve already tried the steps you suggested, but unfortunately, the issue remains unresolved. It’s currently affecting only one mailbox, and we’ve attempted several workarounds to address it. However, the problem still persists.

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  2. Anonymous
    2025-06-12T17:01:36+00:00

    Dear U_Nuwan, 

    Nice to meet you! 

    Thank you for reaching out to Microsoft Community. 

    We can see that that you're experiencing an issue where Outlook, when operating in Cached Exchange Mode, does not update emails automatically unless the application is restarted. We appreciate your detailed description and are here to help. 

    Cached Exchange Mode stores a local copy of your mailbox in an OST file and periodically syncs changes with the Exchange server. When Outlook fails to automatically fetch new messages, it’s typically due to one or more of the following reasons: 

    • Corrupt or misconfigured OST file
    • Disabled or delayed Send/Receive schedule
    • Interference from Outlook add-ins
    • Outdated Outlook build or profile inconsistency

    The fact that Online Mode works properly confirms that the issue lies specifically with local cache sync behavior rather than server connectivity. 

    Please try following steps below to address the issue: 

    1. Check Send/Receive Settings 
      • In Outlook, go to: File > Options > Advanced > Send/Receive…
      • Ensure that "Schedule an automatic send/receive every X minutes" is checked (suggest 5-10 minutes).
      • Click Close to apply.
    2. Rebuild the OST File 
      • Exit Outlook.
      • Navigate to: %localappdata%\Microsoft\Outlook\
      • Locate and rename the .ost file (e.g., append .old).
      • Restart Outlook, which will generate a fresh OST and begin re-syncing.
    3. Disable Problematic Add-ins 
      • Launch Outlook in Safe Mode: Press Win+R, type Outlook.exe /safe and press Enter.
      • If the issue disappears, disable add-ins under File > Options > Add-ins and re-enable one at a time to identify the culprit.
    4. Create a New Outlook Profile 
      • From Control Panel > Mail > Show Profiles, create a new profile.
      • Add your email account and set this profile as default.

    If you require more in-depth guidance or support for these steps, you may also contact Microsoft’s higher-level technical support through:       

    Please let us know if you need further clarification or assistance. We appreciate your patience and look forward to assisting you further.    

    Looking forward to your reply. We hope you have a great day! 

    Warm Regards,    

    Chris-DKN - MSFT | Microsoft Community Support Specialist.

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