When users want to use their client application to find recipient information, they can select from available address lists. Several address lists, such as the GAL, are created by default. Exchange 2007 contains the following default address lists, which are then automatically populated with new users, contacts, groups, or rooms as they are added to your organization:

• All Contacts   This address list contains all mail-enabled contacts in your organization. Mail-enabled contacts are those recipients who have an external e-mail address. If you want mail-enabled contact information to be available to all users in your organization, you must include the contact in the GAL. To learn more about mail contacts, see Understanding Recipients.
  
• All Groups   This address list contains all mail-enabled groups in your organization. Mail-enabled groups are a group of recipients that are created to expedite the mass e-mailing of messages and other information. When an e-mail message is sent to a mail-enabled group, all members of that list receive a copy of the message. To learn more about mail-enabled groups, see Understanding Recipients.
  
• All Rooms   This address list contains all resources that have been designated as a room in your organization. Rooms are resources in your organization that can be scheduled by sending a meeting request from a client application. The user account that is associated with a room is disabled. For instructions about how to add resource mailboxes to an address list, see How to Add a Resource Mailbox to an Address List. To learn more about resource mailboxes, see Understanding Recipients
  
• All Users   This address list contains all mail-enabled users in your organization. A mail-enabled user represents a user outside your Exchange organization. Each mail-enabled user has an external e-mail address. All messages sent to mail-enabled users are routed to this external e-mail address. A mail-enabled user is similar to a mail contact, except that a mail-enabled user has Active Directory logon credentials and can access resources. To learn more about mail-enabled users, see Understanding Recipients.
  
• Default Global Address List   This address list contains all mail-enabled users, contacts, groups, or rooms in the organization. During setup, Exchange creates various default address lists. The most familiar address list is the GAL. By default, the GAL contains all recipients in an Exchange organization. In other words, any mailbox-enabled or mail-enabled object in an Active Directory forest that has Exchange installed is listed in the GAL. For ease of use, the GAL is organized by name, not by e-mail address. For more information, see Managing Global Address Lists.
  
• Public Folders   This address list contains all public folders in your organization. Access permissions determine who can view and use the folders. Public folders are stored on computers running Exchange. For more information about public folders, see Managing Public Folders.
  

An Exchange organization can contain thousands of recipients. If you compile all your recipients in the default address lists, those lists could become quite large. To prevent this, you can create custom address lists to help users in your organization find what they are looking for more easily.

For example, consider a company that has two large divisions and one Exchange organization. One division, named Fourth Coffee, imports and sells coffee beans. The other division, Contoso, Ltd, underwrites insurance policies. For most day-to-day activities, the employees at Fourth Coffee do not communicate with the employees at Contoso, Ltd. Therefore, to make it easier for employees to find recipients who exist only in their division, you can create two new custom address lists—one for Fourth Coffee and one for Contoso, Ltd. When searching for recipients in their division, these custom address lists allow employees to select only the address list that is specific to their division. However, if an employee is unsure about the division in which the recipient exists, the employee can search within the GAL, which contains all recipients in both divisions.

You can also create subcategories of address lists called hierarchical address lists. For example, you can create an address list that contains all recipients in Manchester and another that contains all recipients in Stuttgart. called Research and Development within the Manchester address list container that contains all employees who work in Manchester's Research and Development department.

Although address lists are useful tools for users, poorly planned address lists can cause frustration. To make sure that your address lists are practical for users, consider the following best practices:

• Avoid creating so many address lists that users will not be sure in which list to search for recipients.
  
• Name your address lists in such a way that, when users glance at them, they will know immediately which recipient types are contained in the list. If you have difficulty naming your address lists, create fewer lists and remind users that they can find anyone in your organization by using the GAL.
  

For detailed instructions about creating an address list, see How to Create an Address List.

The following are improvements to address lists in Exchange 2007:

• No longer dependent on the Recipient Update Service   In earlier versions of Exchange, the Recipient Update Service (a component in the Exchange System Attendant service) updated the address lists and e-mail addresses in Active Directory. In Exchange 2007, changes to e-mail addresses and address lists are applied directly to Active Directory. As a result, when changes are made to address lists, you can immediately see the changes in Active Directory Users and Computers without having to wait for RUS to perform the update.
  
• Simplified precanned filters   In Exchange Server 2003 and Exchange 2000 Server, the graphical user interface (GUI) for filtering address lists was complex, containing nested lists that had hundreds of properties. In Exchange Server 2007, the most common filters are defined as precanned filters, which contain a simple and intuitive filter control.
  
• Easier custom-filter construction with OPATH filters   For the few administrators that require advanced filtering requirements not met by precanned filters, you can create custom filters that can be defined by using the OPath filter syntax in the Exchange Management Shell. OPath is a querying language designed to query object data sources. For more information, see How to Create an Address List By Using Recipient Filters.
  
• Ability to filter recipient properties   Exchange 2007 allows you to filter the results of a command by using the recipient type. For example, the Get-User, Get-Recipient, Get-Mailbox, Get-MailUser, Get-Contact, Get-MailContact, Get-Group, Get-DistributionGroup, and Get-DynamicDistributionGroup cmdlets all have a Filter parameter with which you can specify the users or groups to retrieve with the command. When combined with the Set-Address List or New-AddressList cmdlets, you can specify a set of users or groups to retrieve by using a filter string. This type of filter does not modify any configuration or attributes of objects. It only modifies the set of objects that the command returns. For more information about how to create filters in recipient commands, see Creating Filters in Recipient Commands.
  
• Ability to schedule application of address lists at a later time   In Exchange 2007, you can specify when changes to the address list should be applied. You can also specify the amount of time that the tasks should run. For more information, see How to Edit an Address List.
  

For more information about address lists, see the following topics:

• Managing Address Lists
  
• Managing Global Address Lists