A strong point of Outlook application development is the program's ability to make folders available on line and off line. If your application requires both online and offline use, you will need to make the folder and any custom forms contained in it available for offline use. For an example of an application that operates on line and off line, see Chapter 12. "The Northwind Contact Management Application." By using some of the new properties and methods in the Outlook 2002 object model, you can make a folder available for offline use programmatically. For information about programming the Application Folders Send/Receive group, see Chapter 11.
Before you can make a folder available for offline use, you must create an offline folder file (.ost). An offline folder file acts as a local copy of folders in your mailbox or in the public folders in your Favorites folder. Access to an offline folder file requires authentication. You cannot create an offline folder file if you are not connected to an Exchange server.
To create an offline folder file (.ost)
1. On the Tools menu, click E-Mail Accounts, select the View Or Change Existing E-Mail Accounts option, and then click Next.
2. In the Outlook Processes E-Mail For These Accounts In The Following Order list, click Microsoft Exchange Server, and then click Change.
3. Click More Settings.
4. Click the Advanced tab, and then click Offline Folder File Settings.
5. In the File box, type the path to the file you want to use as the offline folder file. The default filename is outlook.ost. If this file already exists, you will be prompted for a new name.
6. Click OK to dismiss the Microsoft Exchange Server dialog box.
7. Click Next, and then click Finish.
Custom forms in folders are not automatically available when off line. If you want custom forms to be available off line, select the Synchronize Forms box, as shown in Figure 8-31.
To specify folders for offline use
1. On the Tools menu, point to Send/Receive Settings, and then click Define Send/Receive Groups.
2. In the Group Name list box shown in Figure 8-38, click a Send/Receive group containing an Exchange Server account, and then click Edit. The default Send/Receive Group is All Accounts.
3. Under Accounts, select your Exchange Server account.
4. In the list, select the folders that you want to use off line in addition to your default folders, as shown in Figure 8-38.
5. If you want to apply a filter to a specific folder, click the folder, click Filter Selected Folder, and then select the options that you want. Filters are an important means of restricting the number of items in an offline folder.
6. If you want to limit the size of messages to download when you synchronize folders, click Limit Message Size, and then click the options that you want.
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