The Outlook add-in is designed to function as a business inbox in Outlook, based on the standard Business Central online. If you're using a different type of deployment, such as a solution that is part of the Embed App program, then you must set up an Azure Key Vault and specify secrets for TEMPORARYDOCUMENTSTORAGEACCOUNT and TEMPORARYDOCUMENTSTORAGEKEY. For more information, see Using Key Vault Secrets in Business Central Extensions.