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How to Fix Shared Mailbox not working in new Outlook Issue?

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    Summary: You may face issues when trying to access shared mailbox in Outlook. In this post, you will know the causes behind the shared mailbox not working in Outlook issue and the solutions to troubleshoot and fix this problem. Also, you’ll find about an OST to PST converter that can help extract mail items if the OST becomes inaccessible or orphaned

    Shared mailboxes in Microsoft Outlook enable team collaboration and faster response to queries and emails. Sometimes, users encounter issues when trying to access shared mailboxes in Outlook. The Shared mailbox is not working or updating issue can occur due to various reasons. In this post, you will learn the reasons behind this issue and the solutions to troubleshoot and resolve it.

    Reasons behind Shared Mailbox not Working in Outlook Issue

    Below are some common reasons that can cause shared mailboxes not working issue in new Outlook:

    • Unstable or weak network or internet connection
    • Lack of permissions or rights to access the shared mailbox
    • Corrupt Outlook email profile
    • Outdated Outlook client and/or Windows OS
    • Oversized or inconsistent Outlook cache (.ost)
    • Conflict with firewalls or antivirus
    • Faulty or incompatible third-party add-ins

    Solutions to Troubleshoot and Resolve the Shared Mailbox not Working in Outlook Issue

    Follow the below solutions to troubleshoot and resolve the shared mailbox not working issue.

    1. Check Permissions

    Check and verify if you have permissions and rights to open and access the shared mailbox. This setting is managed by the IT administrator of your organization. In case you are not able to add a shared mailbox or getting errors while adding the shared mailbox, reach out to your administrator for help.

    2. Restart Outlook and Re-Add Shared Mailbox

    Make sure to close all Outlook processes, including Lync, Skype, or any other MS Office app. Then, wait for a few seconds and start Outlook. This may fix any sync or connection issue that could be causing the issue with the shared mailbox.

    Additionally, you can reconnect the shared mailbox by following these steps:  

    • In Outlook, go to File > Info > Account Settings > Account Settings.
    • Select the Outlook 365 email account and click Change.
    • Click More Settings.
    • Then, click on the Advanced tab.
    • Click Add and then enter the name or complete address of the shared mailbox. Click OK.
    Complete Address of Shared Mailbox
    • If you have permissions, the shared mailbox will be added in Outlook and you should be able to access it.

    3. Update Outlook and Windows

    Make sure Outlook client and Windows operating system are up-to-date. These updates often bring patches and features that are required for secure communication with the Microsoft 365 server. The steps to update Outlook are as follows:

    • Open Outlook.
    • Navigate to File > Office Account > Update Options and click Update Now to check for any available updates.
    Update Now MS Office
    • If available, continue to follow the on-screen instructions to download and install the latest Outlook updates.
    • Also, open Settings > Windows Update and then check and install the Windows operating system updates.
    • After the update, restart the system and check if the shared mailbox is now syncing properly.

    4. Clear RoamCache Files

    If the RoamCache is corrupt or damaged, it may interfere with Outlook functioning and prevent shared mailbox synchronization. However, you can delete the RoamCache and temporary files to troubleshoot this issue. The steps to clear the RoamCache files are as follows:

    • Close Outlook and press Windows key + R.
    • Type %temp% and press Enter.
    Clear Cache in Outlook
    • Select all files and folders in the Temp folder and delete them.
    • Press Windows + R again and this time type %appdata% and click OK. Delete all the temporary files and folders related to MS Office.
    Temp Folder in Outlook
    • Press Windows + R one more time and then paste this path %localappdata/Microsoft/Outlook.
    • Press the Enter key. This opens the location where the RoamCache folder is located.
    • Select and delete the RoamCache folder. Alternatively, you can also rename it to RoamCache_BAK or RoamCache_old.
    RoamCache in Outlook
    • Once cleared, restart your system and launch Outlook.
    • Check if the shared mailbox is now syncing properly.

    5. Create a New Outlook Profile

    Damaged or corrupt profile may conflict with the server communication and may lead to sync issues that can prevent shared mailboxes from working properly in Outlook. To troubleshoot, you can create a new profile and then set up your email account under this new profile. The steps are as follows:

    • Close Outlook and start Control Panel.
    • Navigate to User Accounts > Mail and click on the Show Profiles button.
    • Then, click Add.
    Show Profile Option in Outlook
    • Type any name for this new profile and click OK.
    Create New profile option in Outlook
    • You will see a sign in wizard. Enter your Outlook 365 email accounts details, such as username (email) and password to log in.
    • Once the sign-in is successful, restart Outlook.
    • You will see a dropdown from where you need to choose your new profile and click OK.
    • This will start your email account in the new profile.
    • Now, click File > Info > Account Settings > Account Settings.
    • Select your email account (under new profile) and click Change.
    • Click More Settings > Advanced and then add your shared mailbox.

    6. Recreate Outlook Cache (.OST)

    Since shared mailbox receives a large number of emails every day, it can quickly inflate the OST file. Therefore, it’s important to keep an eye on the local mailbox size (OST) for consistent performance. When this OST file grows large or gets oversized, it may become inconsistent, preventing Outlook from storing any new data that can cause issue and errors. In such a case, you can try to rebuild the OST file. Below are the steps to recreate the OST file:

    • Close Outlook (if running), press Windows + R, and type Control Panel. Press the Enter key or click OK to openthe Control Panel.
    • In the Control Panel, click User Accounts > Mail (Microsoft Outlook) and thenclick on the Data Files tab.
    Show Profile Option in Outlook 1
    • Select the Outlook (.OST) data file or email account where you are having issues with shared mailbox and click Open File Location.
    • You will see the OST file location in a new File Explorer window. Select the OST file and then rename it with the .bak suffix. If the file name is abc@xyz.com.ost, rename it to abc@xyz.com.ost.bak.
    Save location of OST file
    • After creating backup of the original OST file, close all the windows and start Outlook.
    • Outlook will create a new OST file at the same location and start synchronizing/downloading all mail items, such as emails, contacts, attachments, and calendar items, from the mail server to the new OST file.
    • You can add the shared mailbox at this stage but uncheck the Download shared folders option to prevent OST file oversizing.
    Download Shared option in Outlook
    • Click OK.


    You can troubleshoot and resolve the issues with a shared mailbox in the new Outlook by following the solutions discussed in this post. You can also disable the downloading of shared mailboxes, especially if you have a system with moderate specifications. Outlook requires more processing power and resources to process (read/write) large or oversized OST files. Low resources can lead to performance issues and sync issues leading to problems such as shared mailbox not working in Outlook.

    In case the OST file becomes inaccessible or orphaned, you can use an OST to PST converter tool, such as Stellar Converter for OST to extract and restore all mail items to a local PST file or export OST items directly to a live Exchange mailbox or Microsoft 365 account.

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    About The Author

    Shelly Bhardwaj linkdin

    I am a Product Consultant and is associated with Stellar Data Recovery from last 8 years. I write about the latest technology tips and provide custom solutions related to Exchange Server, Office 365, MS Outlook, and many other Email Clients & different flavors of OS Servers. Read More

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