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Published September 15, 2017

What is Cached Exchange Mode in MS Outlook?

Microsoft allows users to work on email application using a combination of MS Outlook and MS Exchange application. This can be done using “cached Exchange mode” for the client-server email communications.

By enabling this option, MS Outlook is triggered to create an OST file for the Exchange mailbox to which it is configured.

It can be considered as an amalgamation of working offline and online where client application (Outlook) continuously sync email data from the server running in the background while processing the user-end actions in the local cache.

While creating an Exchange profile configuration with MS Outlook, this Cached Exchange mode can be enabled. If you already have a profile, changes in its properties can be done to use this offline mode.

How This Cached Exchange Mode Works?

When this Cached Exchange mode is enabled, this option will lead to a generation of OST file which will be the local cache file to hold all the email data of MS Outlook application synced with Exchange mailbox.

You can send or receive the emails from Outlook OST file and when the network is connected, the emails will be synced with the Exchange account. In this way, a local replica of the Exchange mailbox will be maintained offline.

This OST file can also be accessed when offline and hence you will not require being connected to the Exchange network always.

When we talk about Outlook cached Exchange mode enabled, the storage file which comes to our mind is OST file which comprises of the Exchange mailbox emails. Most of the home and personal accounts are not part of Exchange.

How to Enable Cached Exchange Mode?

Open the MS Outlook application with the Exchange profile.

  1. Go to File > Account Settings and then click Account Settings.
  2. Another window will open, here on the Email tab select the Exchange account and click on Change option.
  3. Under Microsoft Exchange Server, check the checkbox available for option “Use Cached Exchange Mode“.
  4. Exit and Restart the MS Outlook application.
  5. While using Cached Exchange Mode, it is possible the messages are stuck in the Outbox; it is advice to perform the Send/Receive operation by clicking on Send All option so that the messages are sent without any complications.

Why Are Users Unable to Turn On Cached Exchange Mode?

There can be several reasons why Cached Exchange Mode is unable to turn on. These reasons can be at user’s end or because of administrator’s settings. Some of these reasons are;

  • Exchange account is not available in the Microsoft Outlook profile.
  • Exchange server administrator has disabled this function.
  • MS terminal services are installed which does not allow this option to apply.

Many times despite the Cached Exchange Mode enabled, emails do not sync and show synchronization issues. This can be caused due to various reasons like server or network issues or Outlook program issues.


The facility of working offline is beneficial for users for continuity of work where Exchange network is unavailable. It triggers the generation of OST file which stores the mailbox email items altogether in the same file which can be accessed easily without needing the network.

It can be done using the Cache Exchanged Mode in MS Outlook for Exchange profile. The method available in the article describes the way of enabling this option.