One of the features of Outlook and Exchange Server Information Services is the ability for end users to work in an offline mode. This can be beneficial when connections cannot be made to the server for various reasons.  Working in an offline mode allows workers to continue to be able to create emails and schedule other email functions that can be completed at the next connection with the email server.

End users are able to work with folders in an offline mode. Sometimes this is required when the network connection is not available. After the network connection is made available then the end users can synchronize their changes and updates with the email server.

Offline folder files (OST) are stored locally on disk in the end user’s Windows folder and are always available. Like other folder files, the offline folder file can be compacted to save space. The offline folder file is created as a mirror image of the end user’s files on the Exchange server. The files are coordinated with each other during synchronization with the server. When creating an offline folder file for the first time it is required that the client is connected to the Exchange Server for the successful creation and synchronization of the Offline Folder file.

An offline folder file can be created as outlined below:

1. From the Tools menu, select Services. (A Services dialog box will be displayed.)
2. Select Microsoft Exchange Server and then click the Properties button.
3. Next click on the Advanced tab and then select the Offline Folder File Settings button. (An Offline Folder File Settings dialog box will be displayed.)
4. In the File box, type the path of the file you want to use as the offline folder file.
5. If the message stating that the “<path><filename>.ost could not be found. Would you like to create it?” appears, click OK or hit enter.
6. Click OK or hit enter twice.

As previously mentioned, end users can add, remove and make changes to their offline folder content as if they were connected to their server even without a connection. Users will have the ability to create replies and read messages in the offline Inbox. They’ll also be able to “send” messages. But these actions will not be applied until the next time the user connects to the email server and performs synchronization.

Messages are still being processed on the email server and those messages that an end user receives will go into the users Inbox for viewing at a later time once synchronization has completed.

The end user can use their synchronization command from the Tools menu to perform the synchronization once the connection is made. Folder changes will be applied such that any deletes of emails performed in the offline folder will occur on the server folder to keep both folders in sync with one another.

Standard Outlook folders such as Inbox, Outbox, Deleted Items, Sent Items, Calendar, Contacts, Journal, Notes, and Tasks can be used in offline mode. End users can choose which files to include for offline work and which files not to include.

Public Folders and any user defined folders can be selected or deselected for offline use. User-defined folders can be selected for offline use by following the steps outlined below.

1. Select the user-defined folder that you wish to allow offline mode capability.
2. Right click on the user-defined folder and select Properties.
3. Click the Synchronization Tab.
4. Select “When offline or online” from the “This folder is available” section.
5. Click OK or hit enter.

If the OST file has been used with a different mailbox you will be prevented from selecting it for offline mode. If you attempt to do so then the following error message is displayed:

“The file <filename>.ost cannot be accessed because it has been configured for use with a different mailbox.”

An administrator might decide to limit which folders can be used in offline mode and which cannot so as to limit a company’s exposure to unforeseen risks should confidential company information be accessed by competitors or non-employees. These decisions can be implemented in the form of policies and rules which must be conveyed to company employees to protect vital company information. Administrators must take this potential exposure into consideration when formulating an offline mode policy.