Cached Versus Online Mode – Which One Is Better For You?

Authored by Casper Manes

Various configuration scenarios fit companies differently. Whether your Outlook users will be using cached or online mode depends on a wide range of factors.

Companies using Exchange Server are often confused around whether they should run cached mode or online mode on their Outlook clients. In this post, we are going to look at just what the differences are, and make some recommendations on when each is appropriate.

What is Cached Mode?

Cached mode, which first came out with Microsoft Outlook 2003, keeps a local copy of the user's mailbox stored on the hard drive as an OST file. Running in cached mode, the Outlook client looks to the local OST file for all access, including reads and searches, while a separate process checks for new mail on the server and syncs data to the local cache.