Administrators are always looking for ways to increase network bandwidth, to increase utilization of their systems or to limit applications from overusing all of their server resources.

If you’re running Outlook and also you are using Exchange Server as your email server then you’ll be interested in hearing about a setting which will prevent Outlook from always having to call out to Exchange server for new email messages.

The setting is called, “Cached Exchange Mode” and it is used to modify how data is pulled down from the Microsoft Exchange email server.

Using Cached Exchange Mode allows your users to keep a copy of their mailbox stored on their computer. By having a local copy of their mailbox stored on their computer your end users will be able to work on their emails even while not connected to the email server. And emails that have been replied to and email messages that have been sent will occur at the next opportunity to synchronize with the email server. This feature allows users to still be productive though they are not connected to their email server.

Problems can however still occur that are related to the synchronization process or configuration settings. Some, not all, of these problems are discussed here.

Some add-ins or front ends to Outlook may store their data locally while others rely on the data stored within Outlook. To provide for faster access to data some add-ins will index the Outlook data. But this process can slow down a server if the flow of email is continuous and indexing is constant. Complaints can soon follow if the network becomes overloaded and/or CPU resources become spread too thin.  So if you wish to avoid these problems then here is how you can turn on Cached Exchange Mode:

For Outlook 2007 follow these steps:

1. From Outlook go to the Tools Menu and choose Account Settings
2. Verify that the “Email” tab is selected; if not then do so now
3. Double click on the email account you wish to change
4. Check the check box labeled “Use Cached Exchange Mode”

For Outlook 2003 follow these steps:

1. From Outlook go to the Tools Menu and choose Email Accounts
2. Choose “View or change existing account”
3. Select the Exchange account you wish to change and select “Change”
4. Check the check box labeled “Cached Exchange Mode”

Restart Outlook for the changes to activate the changes.

If you are unable to change this configuration setting then you will need the assistance of an administrator. Note that if you do not see the “Cached Exchange Mode” option then you are not using an Exchange email account.  Again, contact an administrator for further assistance.

These days everyone has mobile hand held devices and most corporate users like to be able to read their email from their mobile device. There are a lot of users who will synchronize their Windows mobile devices with Outlook using ActiveSync. But some may report problems with Cached Exchange Mode when they sync their online data with the offline cache.  Such problems include long synchronization delays and long synchronization completion times.

The long synchronization times might be a symptom of how Cached Exchange Mode is configured. Specifically the cause might be if Cached Exchange Mode has been configured to download headers before downloading full items during the synchronization process in Outlook. The problem will manifest itself during the synchronization process when Outlook is receiving the headers. What happens is that ActiveSync becomes activated and overrides the Cached Exchange Mode settings. The result is that not only are the headers downloaded but also each email message’s full items. And since this is done in a serial manner then your end users will experience long download times.

An administrator can correct this problem by making the following small adjustment:

1. From the File menu select Cached Exchange Mode
2. Click on “Download Full Items”
3. Then Exit

No restart of Outlook is necessary for this change to take effect.

There are some things to consider when choosing “Download Full Items” versus “Download Headers”. If you have enough network bandwidth available then you’ll probably want to choose the “Download Full Items” option. For instance, while connecting to your email server while at the office using their high speed connections. But if you are being charged for your connection times then the “Download Headers” option would be a good choice as it will reduce how much data is sent during the connection and how much time is used during the connection.

As an administrator, you might want to relay these recommendations to your end user community and communicate to them how best to connect to corporate email servers when they are away from the office and using slower speed connections.