Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.
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To check for cache mode, view the following article and see if this feature is enabled on your Outlook client.
https://support.office.com/en-us/article/Turn-on-Cached-Exchange-Mode-7885af08-9a60-4ec3-850a-e221c1ed0c1c