How do I synchronize the contacts of a Microsoft 365 user with another user?

sync.blue® enables the synchronization of contacts from a specific Exchange Online mailbox (e.g. personal mailbox, shared mailbox, public folder,...) with any number of other personal Exchange Online mailboxes (“address books”).

For this to work, the appropriate mailbox permissions must be assigned, since even an Exchange administrator does not have read/write permissions for all Exchange mailboxes by default. There are two options for this:

1. Manually creating the permissions

2. Creating the permissions with a PowerShell script

Option 1: Manually creating the permissions

In Exchange Admin Center (EAC) the permissions can be set as follows:

1. Log in to the Exchange Admin Center

2. Go to “Users” > “Active Users”.

3. Select the mailbox with which you want to synchronize contacts.

4. In the "Email" tab, select the permission "'Read and Manage' permissions (‎X)".

5. Add the user who is used with sync.blue®. 

Option 2: Creating the permissions with a PowerShell script

A PowerShell script can be used to set up the permissions automatically:

1. Install Power Shell.

2. Define the user that is used with sync.blue® as “syncblueuser”:

$syncblueuser = "m.mustermann@xxx.onmicrosoft.com"

3. Install ExchangeOnlineManagement module:

Install modules -Name ExchangeOnlineManagement

4.  Authorize ExchangeOnlineManagement:

Connect-ExchangeOnline -UserPrincipalName $syncblueuser -ShowProgress $true

5. Define the users in whose accounts the contacts should be synchronized:

Manually:

$users = @("target1@xxx.onmicrosoft.com", "target2@xxx.onmicrosoft.com", "target3@xxx.onmicrosoft.com")

For all users (here a help article on how to automatically create a list of all users):

$users = (Get-Mailbox -ResultSize Unlimited).PrimarySmtpAddress -join ","

6. Grant the defined “syncblueuser” the necessary access permissions to the specified users:

foreach ($user in $users) {
 Add-MailboxPermission -Identity $user -User $syncblueuser -AccessRights FullAccess -InheritanceType All
}