You'll need to develop a way to divide your organization into virtual organizations. When making this division, we recommend using the Custom Attribute properties on the mailboxes, contacts, and groups instead of the precanned conditional attributes (such as Company, Department, or State/Province). Using Custom Attributes instead of precanned attributes includes the following benefits:

• Not all recipient types have precanned conditional attributes in Active Directory. For example, the Active Directory objects Distribution Group and Dynamic Distribution Group don’t support the Company, Department, or State/Province attributes.
  
  
• Not all precanned conditional attributes are exposed in cmdlets for some recipients. For example, the Company, Department, and StateOrProvince parameters aren’t available in the cmdlets for mail users, contacts, distribution groups, and mail-enabled public folders.
  
  
• Multiple cmdlets are required to segment recipients when you use precanned conditional attributes. For example, to set the Company, Department, or StateOrProvince parameters for a user mailbox, you must run the Set-User cmdlet after you run the New-Mailbox or Set-Mailbox cmdlets.
  
  However, the CustomAttribute parameters are exposed in the Set-* cmdlets for each recipient type, so there’s no need to also run the Set-User cmdlet.
  
  
• Custom Attribute properties are explicitly reserved to customize an organization and are controlled entirely by organization administrators.
  
  

To learn more about custom attributes, see Understanding Custom Attributes.

Another best practice to consider when dividing your organization is to use company identifiers in the names of distribution groups and dynamic distribution groups. One method for doing this is to use group naming policies. These policies allow you to specify that a prefix, a suffix, or both be applied to distribution group names. This is helpful when dividing your organization because you can use these policies to specify a suffix or prefix based on user attributes such as the creator of the distribution group's Company, State/Province, Department, and Custom Attribute properties. This is especially important if you allow users to create their own distribution groups. For more information, see Create a Distribution Group Naming Policy.

When you create the address lists and GALs, don’t use the IncludedRecipient and ConditionalX parameters, such as ConditionalCompany and ConditionalCustomAttribute5. Instead, we recommend that you use recipient filters. To learn more about recipient filters, see Creating Filters in Recipient Commands.

Create the address lists

When you create the ABP, you include multiple address lists based on how you want your users to view the lists in Outlook or Outlook Web App. This scenario requires four address lists:

• AL_FAB_Users_DGs
  
  
• AL_FAB_Contacts
  
  
• AL_TAIL_Users_DGs
  
  
• AL_TAIL_Contacts
  
  

This example creates the address list AL_TAIL_Users_DGs. The address list contains all users and distribution groups where CustomAttribute15 equals TAIL.

The above command would then be run to create the remaining address lists: AL_FAB_Users_DGs, AL_FAB_Contacts, and AL_TAIL_Contacts.

For detailed syntax and parameter information, see New-AddressList.

To learn more about creating address lists by using recipient filters, see Create an Address List By Using Recipient Filters.

Create the room lists

This scenario requires three room lists:

• AL_FAB_Rooms
  
  
• AL_TAIL_Rooms
  
  
• Default All Rooms (created by default)
  
  

ABPs must contain a room list. If your organization doesn't have resource mailboxes (such as room or equipment mailboxes), we recommend that you create a blank room list. The following example creates the blank room list AL_BlankRoom.

However, in this scenario, Fabrikam and Tailspin Toys both have room mailboxes. This example creates the room list for Tailspin Toys by using a recipient filter where CustomAttribute15 equals TAIL.

The above command would then be run to create the room list for Fabrikam (AL_FAB_Rooms).

For detailed syntax and parameter information, see New-AddressList.

Create the GALs

This scenario requires three GALs:

• GAL_FAB
  
  
• GAL_TAIL
  
  
• Default GAL (created by default)
  
  

The GAL used in an ABP must be a superset of the address lists. Don’t create a GAL with fewer objects than exists in any or all of the address lists in the ABP.

This example creates the GAL for Tailspin Toys. It includes all the recipients that exist in the address lists and room list.

The above command would then be run to create the GAL for Fabrikam (GAL_FAB).

For detailed syntax and parameter information, see New-GlobalAddressList.

Create the OABs

This scenario requires three GALs:

• OAB_FAB
  
  
• OAB_TAIL
  
  
• Default OAB (created by default)
  
  

When using the New-OfflineAddressBook or Set-OfflineAddressBook to create the OAB, include the appropriate address lists or GAL in the AddressLists parameter to make sure no entry is unexpectedly missed. For example, if you want to customize the set of lists a user will see when viewing the OAB, or if you simply want to reduce the OAB’s download size, you can use the AddressLists parameter to specify the address lists available to the OAB. However, if you want users to see the full set of GAL entries in OAB, make sure you include the GAL in the AddressLists parameter.

This example creates the OAB for Tailspin Toys. The entire GAL (GAL_TAIL) is included in the OAB..

The above command would then be run to create the OAB for Fabrikam (OAB_FAB).

For detailed syntax and parameter information, see New-OfflineAddressBook.

After all the required lists are created, you can create the ABPs.

This example creates the ABP for Tailspin Toys.

The above command would then be run to create the ABPs for Fabrikam (ABP_FAB) and the organization’s CEO (ABP_CEO).

For detailed syntax and parameter information, see New-AddressBookPolicy.

Assigning the ABPs to users is the last step in the process. ABPs take effect when a user's application connects to the Microsoft Exchange Address Book service on the Client Access server. Users who are already connected to Outlook or Outlook Web App when the ABP is applied to their account will have to close and then restart the client application before they can see their new address lists and GAL.

This example assigns the address book policy ABP_TAIL to all mailboxes where CustomAttribute15 equals TAIL.

For more details, see Assign an Address Book Policy to a Mail User.