Outlook always updating cached messages Local xxx
With Cached Exchange Mode, which is the default setting for users, Outlook no longer depends on continuous network connectivity for access to user information.
When a user is connected, Outlook continuously updates users' mailboxes so that the mailboxes are kept up to date.
Mailbox data is only cached in memory and never written to disk.
Cached Exchange Mode is the preferred configuration in Outlook 2016 and is useful in the following situations: Even when it is configured in Cached Exchange Mode, Outlook 2016 must contact the server directly to do certain operations.
In some cases, you can improve the performance of Cached Exchange Mode for your whole organization or for a group of users—for example, users who work remotely.
To do this, configure the Download shared non-mail folders option in the Office Customization Tool (OCT) when you customize your Cached Exchange Mode deployment.
Note that this setting applies to both mail and nonmail folders in Outlook 2016.
However, by default, when Outlook 2016 is installed and Cached Exchange Mode is enabled, a new compressed version of the Outlook data file (.ost) is created.
The earlier version of the file is kept and, if it is necessary, can be opened by Outlook 2016.
Exchange mail accounts by default use cached exchange mode, which makes Outlook store your recent messages and contacts on your computer for easier access.