We see it’s common to use Office365 in combination with the Active Directory synchronization tool. Even when you have more AD Domains it is possible to sync them to one Azure Active Directory tenant. When you use more AD domains you sometimes want to split the Office365 mail users in different groups and give them an own address list.

Use PowerShell in Office365 Exchange Online

To login on the Exchange online with Powershell use the following commands, use your Office365 admin account;

# Get User Credentials
$UserCredential = Get-Credential
# Create PowerShell session
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
#Import Session
Import-PSSession $Session

Create Global Address List

To create an new Address list in Office365 we are gone use PowerShell, make sure you have created the session descriptor in previous chapter.

# Create SampleA domain GAL
New-GlobalAddressList -Name GAL_SampleA -RecipientFilter {((RecipientType -eq "UserMailbox") -and (UserPrincipalName -like "*@samplea.onmicrosoft.com"))}
# Create SampleB domain GAL
New-GlobalAddressList -Name GAL_SampleA -RecipientFilter {((RecipientType -eq "UserMailbox") -and (UserPrincipalName -like "*@sampleb.onmicrosoft.com"))}

In the Recipient Filter you can use different field to filter on, you can find them all on the Microsoft Technet site here.

Create Address List and Offline Address Book

Before we can make any Address Book Policy to the users we need to have defined an Offline Address Book. The OAB is build out an Address List that needs to be created also.

# Create Address List for SampleA domain
New-AddressList -Name AL_SampleA -RecipientFilter  {((RecipientType -eq "UserMailbox") -and (UserPrincipalName -like "*@samplea.onmicrosoft.com"))}
# Create Offline Address Book for SampleA domain
New-OfflineAddressBook -Name OAB_SampleA -AddressLists AL_SampleA
# Create Address List for SampleB domain
New-AddressList -Name AL_SampleB -RecipientFilter  {((RecipientType -eq "UserMailbox") -and (UserPrincipalName -like "*@sampleb.onmicrosoft.com"))}
# Create Offline Address Book for SampleB domain
New-OfflineAddressBook -Name OAB_SampleB -AddressLists AL_SampleB

With this PowerShell command we have created the Offline Address Book and Address List for both domains. Now we can assign them to the users.

Assign Global Address List to users

Now we have created the new Global Address Lists we need to create an new Address Book Policy to assign them to our mailbox users.

# Create Address Book Policy for domain SampleA
New-AddressBookPolicy -Name "ABP_SampleA” -AddressLists "" -RoomList "\All Rooms" -OfflineAddressBook “\OAB_SampleA” -GlobalAddressList “\GAL_SampleA”
# Create Address Book Policy for domain SampleB
New-AddressBookPolicy -Name "ABP_SampleB” -AddressLists "" -RoomList "\All Rooms" -OfflineAddressBook “\OAB_SampleB” -GlobalAddressList “\GAL_SampleB”

To assign the mailbox user this new policy use the following commands. Edit the command to your own need to specify the right user(s).

Set-Mailbox -Identity testuser@samplea.onmicrosoft.com -AddressBookPolicy "ABP_SampleA"

The Magic off filling the GAL

All the new address books are added and we have assigned them to our test user. You will see our test user has an empty address book , huh? To fill our new Global Address List and Address List we need to ‘change’ each user that needs to be in the address book. I have made an small script to do this;

$mailboxusers = Get-Mailbox -All
$i=0
$count = $mailboxusers.count
Write-Host "Mailboxes found: " $count
foreach($mailbox in $mailboxusers){
$i++
Set-Mailbox $mailbox.alias -SimpleDisplayName $mailbox.SimpleDisplayName -WarningAction silentlyContinue
Write-Output "Mailbox $i from $count changed: $mailbox.UserPrincipalName"
}

With this script actually nothing get changed on the mailbox user, it just touch them so the user appears in the Address Lists. Now open the test user mailbox again and check the Global Address List, it will be filled with the users we just touched.

I found an more advanced script to touch users mailboxes at Microsoft here: link