Click Next > Finish and restart Outlook.

Click the Use Cached Exchange Mode option to download email to an Outlook data file and select the time using the slider.Choose Office 365/Microsoft 365 or Exchange email and click Change.Open Microsoft Outlook and click File > Account Settings > Account Settings.The steps to enable Cached Exchange Mode are as follows:

If the Cached Exchange Mode is disabled, you may encounter such errors while opening or expanding the mailboxes. It provides a better user experience and Outlook performance. Enable the Cached Exchange ModeĬached Exchange Mode is highly recommended if you use Exchange or Microsoft 365 email accounts in Outlook. Solutions to Fix the Outlook Error “Unable to expand the folder, Client operation failed”įollow the below solutions and workarounds to troubleshoot and fix the error in Microsoft Outlook 2021, 2019, 2016, 2013, and 2010.

Oversized or large Outlook data file (OST).

Reasons for ‘Unable to expand the folder, Client operation failed’ Errorįollowing are some common reasons that may lead to the ‘Unable to expand the folder’ error and prevent Outlook users from accessing messages or mail items.

In this article, you will learn the reasons that can prevent you from expanding Outlook folders and the solutions to resolve the issue. Microsoft Outlook cannot access the specified folder.’ The error prevents you from expanding or opening the mail folders and accessing the messages. But sometimes, when you try to expand shared folders, public folders, or a mail folder from the secondary mailbox to access the mail items or view emails, you may encounter an error message, ‘Unable to expand the folder, Client operation failed’ or ‘Cannot expand the folder. In Outlook, you can add shared folders, public folders, or secondary mailboxes and access all the mail folders and items in them.

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