Configuring a Hierarchical Address Book in Exchange Server

In an Exchange Server organization the address book that users see in Outlook is basically just a flat, alphabetical list of names. There’s no easy way to look at the address book and work out the structure of the organization, or to tell who the most senior people are within a group. It’s easy to think that “ranking” within an organization is an ego thing, the reality is that it’s important in many situations to be able to quickly identify organizational structure and know who reports to who.

Exchange supports the need for visibility of an organizational structure with a feature called the hierarchical address book (HAB). Let’s take a look at a simple example of how to implement hierarchical address books in an Exchange organization, using the following org structure.

The hierarchical address book is made up of a series of distribution groups that are nested in a way that matches the org structure. The distribution groups can be located anywhere you like in Active Directory, but it’s useful to place them into a dedicated OU so that there’s no confusion about their purpose. For this example I’m using an OU called “Hierarchical Address Book”.

Create the first distribution group that will be used as the root of the hierarchy.

[PS] C:\>New-DistributionGroup "Exchange Server Pro" -OrganizationalUnit "Hierarchical Address Book"

Name                          DisplayName                   GroupType                     PrimarySmtpAddress
----                          -----------                   ---------                     ------------------
Exchange Server Pro           Exchange Server Pro           Universal                     ExchangeServerPro@exchange...

Configure the group to be used as a hierarchical group by running the Set-Group cmdlet.

[PS] C:\>Set-Group "Exchange Server Pro" -IsHierarchicalGroup $true

Then enable the Exchange organization to use the group as the root of the hierarchy.

[PS] C:\>Set-OrganizationConfig -HierarchicalAddressBookRoot "Exchange Server Pro"

The changes will appear in Outlook after the offline address book has updated and been downloaded by Outlook, so don’t expect to see the results immediately. In fact, if you don’t want to display an incomplete hierarchy to your users, just wait until you’ve set up all of the groups first before you enable the hierarchical address book. If you do enable it now, when everything has been updated a new “Organization” tab will appear in the address book in Outlook.

With the root of the hierarchical address book working, the next steps are to create the rest of the groups that represent the org structure, and nest them accordingly. By placing all the groups in the same OU as the first one, a single PowerShell command can be run to configure them all as hierarchical groups.

[PS] C:\>Get-Group -OrganizationalUnit "Hierarchical Address Book" | Where {!($_.IsHierarchicalGroup)} | Set-Group -IsHierarchicalGroup $true

After the address book has had time to update, the new hierarchy is visible for Outlook users.

For some organizations, the default ordering of the groups in the hierarchical address book will not be suitable. In the example shown above, the organization would prefer that the Executive group appeared at the top of the list, instead of the bottom. This can be achieved by setting the seniority index on the groups. By default there is no seniority index configured on groups, but you can configure a value of up to 100, with 100 being the most senior.

[PS] C:\>Set-Group "Executive" -SeniorityIndex 100

[PS] C:\>Set-Group "Sales and Marketing" -SeniorityIndex 50

Seniority can also be configured within a group, for example if you would like the manager of a team to appear at the top of the list instead of the group members being sorted in alphabetical order.

[PS] C:\>Set-User adam.wally -SeniorityIndex 100

Managing the hierarchical address book is an ongoing process, not a simple one-time setup. This is particularly true of larger organizations that have a higher rate of change in the organizational structure as departments are reshuffled, people change roles, or people leave the company entirely. Maintaining the hierarchical address book needs to be baked into your workflow, for example when a person becomes the manager of a team you can update the configuration of their seniority index.

There are also some group policy controls for the hierarchical address book. One in particular should be considered – the disabling of department selection. Because of the nesting of distribution groups to form the hierarchical address book, a person who sends an email to a top-level group might not realize they are sending an email to every child group as well. You can block that behavior by enabling the “Turn off the Hierarchical Address Book department selection” in the Outlook 2016 group policy administrative template (found under Account Settings/Exchange). However, if you do need department selection to remain enabled, consider putting in place some restrictions on who can send to larger distribution groups in your organization.