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How to Sync the Global Address List Between Two Tenants

Update 2024

CiraApps has streamlined the process of synchronizing Global Address Lists (GALs) across multiple tenants. Users can now perform this sync seamlessly with CiraHub.

Sync Multiple Global Address Lists with CiraHub (Preferred Method)

CiraHub offers an efficient and user-friendly solution for multiple Microsoft 365 and Exchange GALs between tenants. It also provides advanced tools, such as field mapping, which intelligently identifies and merges duplicate entries, preserving data integrity and ensuring that contact information remains accurate and up-to-date. With CiraHub, Microsoft 365 and Exchange users can streamline their contact management processes, saving time and reducing the risk of errors from performing manual synchronization.

How CiraHub’s Multi-Way GAL Sync Works

CiraHub uses a unique model to streamline sync or merge multiple GALs. At the core of the model is the central „Hub,“ which serves as a primary repository for all contact data. Each GAL represents a „spoke“ that connects to the Hub. Think of these spokes as individual contact lists, each serving a specific department, division, or location within the organization. By linking multiple spokes to the Hub, CiraHub allows everyone to have access to the same information.

When a change is made to a contact in one GAL, CiraHub automatically makes that update to the Hub and then distributes it to all connected spokes. This real-time synchronization guarantees that everyone in the organization has access to the latest contact information, regardless of which GAL they are using.

CiraHub’s multi-way GAL sync also offers advanced customization options. Admins can define specific sync rules and filters to control which contacts are shared between different GALs. This allows organizations to maintain a high level of privacy and security, ensuring that sensitive information is only accessible to those who need it.

For organizations looking to sync the Global Address Lists together between two enterprises, check out this Two-Way GAL Sync article on CiraHub.

Prerequisites for Two-Way GAL Sync on CiraHub

To perform a multi-way GAL sync on CiraHub, ensure that you have the following:

  • Access to the CiraHub dashboard via a paid license or free trial
  • Administrative rights to your organization(s) Microsoft 365 GAL

Basic Steps For Multi-Way GAL Sync

Syncing GAL to GAL with CiraHub is a straightforward process:

  • Create a Microsoft 365 GAL Spoke: On the CiraHub dashboard, create a Spoke for your first Microsoft 365 GAL. Securely log in to your GAL account and connect it to CiraHub. This step will involve authenticating your organization’s contact repository, such as Admin Exchange or Office 365 accounts.
  • Add Another Spoke: You’ll need to create an additional Spoke for another GAL and establish the connection with the Hub.
  • Initiate GAL-to-GAL Sync: On the CiraHub dashboard, select “Sync Now” to begin synchronizing contacts between the two GALs, enabling bi-directional data flow. This process will ensure that any changes in the GAL are promptly reflected in the second tool and vice-versa.

Alternative: Multi-Way GAL Sync With CiraSync

This guide shows how to use CiraSync Enterprise Edition to sync the Global Address List (GAL) between two Office 365 tenants.

NOTE: This guide uses Tenant A and Tenant B as examples.

If you are an on-premise Exchange user, learn how to share contacts between two Exchange organizations on itrezzo!

Before You Start

This guide assumes that a dedicated service account with Impersonation Mode has been set for the CiraSync tenants involved with this procedure. Without an administrator account with Application Impersonation, CiraSync will be unable to push contact and calendar updates to user mailboxes. Check out the following articles to learn how to set up a dedicated service account with the appropriate permissions for all of your tenants and then return here to learn how to sync the GAL between multiple tenants with CiraSync Enterprise Edition:

  1. Setting up a Dedicated Service Account for CiraSync in Office 365
  2. Setting Impersonation Mode to Sync to User Mailboxes
  3. Making CiraSync Use a Specific Office 365 Service Account


Creating a User Mailbox

NOTE: This user mailbox will contain GAL contents of Tenant A. Therefore, this user mailbox should not be accessed or used by users to minimize alterations to the mailbox content.

  1. Launch the Office 365 Admin Portal of Tenant A.
  2. Click Users > Active Users in the left navigation panel.
  3. Click +Add a user at the top of the page. The Add new user panel will appear on the screen. (See figure below.)
  4. Provide a name for this mailbox.
  5. Click Password > Let me create the password.
  6. Create a strong password for the user mailbox.
  7. Uncheck the Make this user change their password when they first sign in box.
  8. Click the slider next to an Exchange Online Plan to assign a Microsoft Exchange License to the mailbox.
    NOTE: The licenses can be any of the following plans in Office 365: Kiosk for $2.00 per month or Microsoft F1/Plan 1 for $4.00 per month.
  9. Click Add at the bottom of the panel.

Syncing the Global Address List to the New User Mailbox

  1. Log in to the CiraSync home dashboard of Tenant A.
  2. Click + in the Contact List pane.
  3. Select the Global Address List as the Contact Source Type.
  4. Follow the wizard to create a sync configuration.
    NOTE: The source will be contacts of the Tenant A GAL, which can be All Mailboxes and/or All Users, a Contact Collection, or a Dynamic Distribution List. The target will be the user mailbox created in Creating a User Mailbox section of this guide.
  5. Perform a manual sync with the Update Cache box checked.

Syncing the Tenant A Global Address List to Tenant B

  1. Log in to the CiraSync home dashboard of Tenant B.
  2. Click the + in the Contact Lists pane. (See figure below.)
  3. Select Shared Mailbox at another Company as the contact source type. (See figure below.)
  4. Type in the user mailbox that was created in the Creating a User Mailbox section of this guide.
  5. Click SIGN IN. (See figure below.)
  6. You will be taken to the Office 365 sign-in page. (See figure below.)
  7. Type in the password of the user mailbox.
  8. Click Sign in. You will be taken to STEP 1: Select Private Folder from another Company. (See figure below.)
  9. Select the Contacts List created from the sync performed in the Syncing the Global Address List to the New User Mailbox section of this guide.
  10. Click NEXT. (See figure below.) You will be taken to STEP 2: Choose target mailboxes. (See figure below.)
  11. Select All Mailboxes to sync Tenant A’s GAL to your users.
  12. Click NEXT. (See figure below.) You will be taken to STEP 3: Specify contact list options. (See figure below.) 
  13. Name the contact list you are about to create in the box under Provide Contact List Name. The contact list name will be added as a category for each contact synced by CiraSync.
    1. Check Sync Contact Groups if you have groups in the contact list and would like to sync members of that group. You may skip to the following step if this is not the case.
    2. Check Populate Outlook Auto-Complete List if you want these sync contacts appear in the Outlook Auto-Complete list. You may skip to the following step if this is not the case.
    3. Click the + next to Contacts, and then name the subfolder to sync to a subfolder. If you would like to sync these contacts to your main Contacts folder, then skip to Step 14.
  14. Click SAVE. (See figure below.) You will be taken to the sync summary dashboard. (See figure below.)
  15. Click the blue back arrow to return to the CiraSync tenant dashboard.
  16. Check the Update Cache box under the Sync Status pane at the top-right corner of the dashboard.
  17. Click SYNC NOW to run a manual sync. (See figure below.)

An there you go! We just synced the Global Address List between two tenants!

NOTE: If Tenant B has to sync their GAL to Tenant A, Tenant A and B will switch roles. Tenant B will follow the steps in the Creating a User Mailbox and Syncing the Global Address List to the New User Mailbox sections of this guide. Tenant A will then follow the steps in the Syncing the Tenant A Global Address List to Tenant B section of this guide.

To directly sync the two GALs without having to create an empty mailbox, check out our new product, CiraHub!

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CTO and Founder of Cira Apps Limited. I have been building Exchange applications and related contact management for 15 years.