In some situations, it is recommended that you turn off cache mode for shared mailboxes. We recommend that you turn off cached mode if:
Please note that there may be some disadvantages in turning off cache mode. Outlook can be experienced as more slowly, and you can no longer work offline
Click on "File"
Click on "account settings"
Click on your email account
Click on "more settings"
Click on "advanced" and remove the tick in the box "download shared folders"