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Cross-forest Migration from Exchange 2013 to 2019/2016

Cross forest migration is the process of migrating mailboxes, data, and other Exchange resources between separate Active Directory forests. This approach is commonly required during mergers, acquisitions, organizational restructuring, or business consolidation when multiple IT environments need to be integrated. Using cross forest migration with Active Directory allows organizations to bring different environments together under a single structure. It simplifies administration, improves resource management, and enhances collaboration across teams while ensuring a smooth migration.

Mailbox migration between different forests can be challenging and time-consuming, especially when relying on native tools. Built-in cross-forest migration methods usually require establishing trust relationships between forests or executing multiple complex PowerShell commands. The process can become even more complicated when migrating from older Exchange versions to newer environments, as additional configuration steps are often required.

EdbMails Exchange Migration Software provides a simple and efficient solution for cross-forest mailbox migration between on-premises Exchange servers. Its intuitive wizard-based interface automates most of the migration process, reducing manual work and lowering the risks commonly associated with traditional migration approaches.

Cross forest Exchange migration

The EdbMails Exchange Migration tool simplifies the process of migrating mailboxes, public folders, archive mailboxes, and shared mailboxes between different Active Directory forests without coexistence complications. It enables direct migration from Exchange versions such as 2010 or 2013 to newer versions like Exchange 2016 or 2019 in just a few clicks, ensuring a smooth and reliable migration experience.

The software is designed for high-performance migration. It includes incremental migration, which migrates only newly added or modified items after the initial migration. This approach saves time and reduces the load on the servers. EdbMails also handles throttling automatically, helping prevent slowdowns and maintaining server stability throughout the migration.

For organizations managing large-scale migrations, EdbMails allows up to 20 mailboxes to be migrated simultaneously, helping complete the process faster. Advanced filtering options give precise control over the migration by allowing you to select items based on date range, sender, recipient, subject, attachments, or message status such as read or unread. This ensures that only the required data is included in the migration.

The upcoming sections will guide you through all essential prerequisites, detailed steps for cross-forest Exchange migration, and important post-migration tasks to complete a successful migration without disruptions.

Cross-forest Migration Challenges and EdbMails Solutions
Challenge 1:
Managing different Cross-forest Migration:In cross-forest Exchange migrations, separate AD environments exist without a trust relationship, making user account matching and mailbox mapping complex.
Solution: EdbMails includes cross forest migration which allows connecting both source and target Exchange servers directly using admin credentials and performs mailbox mapping automatically, eliminating manual matching and minimizing configuration complexity.
Challenge 2:
Large-scale Mailbox Migration:During high-volume mailbox transfers, Exchange and Microsoft 365 can slow down data transfer or cause connection timeouts.
Solution: EdbMails optimizes performance for large-scale migrations through concurrent mailbox migration, smart reconnection, and automatic throttling management to ensure consistent throughput without data loss.

Exchange Cross-forest Migration Prerequisites

Before you migrate to the target server, you need to create a valid mail-enabled user in the target forest with a specified set of Active Directory (AD) attributes. The following table illustrates the coexistence scenarios in various Exchange server versions.

Exchange server version	Coexistence scenario	Requirement	Migration
Exchange 2019	Possible. Can coexist with Exchange 2013 Can coexist with Exchange 2016	Exchange 2013 must have Cumulative Update 21 (CU21) or later Exchange 2016 must have Cumulative Update 11 (CU11) or later	EdbMails Exchange migration software allows you to migrate mailboxes to any Exchange server without worrying about coexistence requirements or limitations.
Exchange 2016	Can coexist with Exchange 2010 and Exchange 2013	Exchange 2010 must have the latest Rollup Update for Service Pack 3 (SP3)Exchange 2013 must have Cumulative Update 10 (CU10) or later

Step 1: Check that your system meets the Exchange server setup requirements.
The following links will help you set up your target Exchange server. Learn more about the network, hardware, coexistence scenarios, and operating system requirements for installing Exchange.
Step 2: Prepare your system with the following prerequisites for Exchange server
Complete the following prerequisites for Active Directory, Windows Mailbox server, and Windows Edge Transport servers before installing the target Exchange server.
Install cumulative updates (CU) on the source Exchange server
For migrating Exchange on-premises to Exchange, it is required that you have the latest cumulative updates (CU) installed on the source server.
1. Install for Exchange server 2016
2. Install for Exchange server 2019
Assign the Organization Management role group in Exchange to the admin user. It is an elevated permission that is required if you want to migrate Public folders.
Step 3: Set up the target Exchange server for migration
Given below is a list of key points for installing and preparing the Exchange server for migration.
1. Prepare AD and domains
  1. Before installing the Exchange server you need to prepare your Active Directory forest and its domains for the new version of Exchange.
  2. If you have a separate team to manage the Active Directory schema, you need to first extend the active directory schema, else proceed to the next step to prepare the Active Directory.
  3. If you have multiple domains you need to additionally prepare the Active Directory domains.
2. Install Exchange server on your computer
  Before installing the Exchange server, ensure that you meet the server system requirements and prerequisites as outlined previously. Next, follow the link to install Exchange 2016 or install Exchange 2019 from the setup wizard based on which server you want to migrate to.
3. Prepare a clean Exchange target environment
  1. Create and configure a send connector to send mail outside the Exchange organization.
  2. By default, Exchange automatically creates receive connectors for inbound mail flow when the mailbox server is installed. If you need to configure receive connectors, follow the steps in the link.
  3. Add accepted domains to allow recipients to send and receive email from another domain.
  4. Configure the default email address policy to add the accepted domain to every recipient in the organization.
  5. Configure external URLs (domains) on the virtual directories in the Client Access (frontend) services on the Mailbox server to allow clients to connect to your server from the internet (outside the organization’s network).
  6. Configure internal URLs on the virtual directories in the Client Access (frontend) services on the Mailbox server to allow clients to connect to your server from the internal network.
  7. Configure SSL certificates from a third-party certificate authority for services such as Outlook Anywhere and Exchange ActiveSync.
  8. Verify the Exchange server installation by running the command Get-ExchangeServer on the Exchange Management Shell (EMS).
4. Create trust relationship between forests (Optional)
  A forest trust is an authentication between two domains within the same Active Directory forest which creates a trust between two root domains for exchanging information. By creating a trust in advance, it is possible to address the trust issues during or after the migration.
5. Create mailboxes and Public folders on the Exchange server
  Before beginning the migration, ensure that mailboxes are available on the target Exchange server. You can opt to let EdbMails automatically create the mailboxes to simplify the process. If you prefer manual creation, please refer to the guidance provided in the links below.
  1. See how to create mailboxes in Exchange server
  2. Steps to create Public folder in Exchange server
6. Assign management roles to the admin account
  Set the following permissions to the admin account on the source and target Exchange server to migrate mailboxes on behalf of other users in your organization.
  - On the source server
    - ApplicationImpersonation
    - View-Only Configuration - Run the cmdlet New-ManagementRoleAssignment using the Exchange Management Shell to assign the View-Only Configuration role to the admin.
  - On the target server
    - Application Impersonation
    - View-Only Recipients
    - View-Only Configuration
7. Verify the mailbox of the admin account
  Check to see if the admin account that has been assigned management roles has a valid and non-hidden mailbox on the Exchange server.
8. Configure the throttling and message-size limits
  Create custom EWS throttling policies and configure message size limits on the Exchange server by following the steps in the links below.
  1. EWS throttling settings on Exchange server
  2. Configure message size limits on Exchange server
If you have deployed the Identity Lifecycle Manager (ILM) to synchronize the cross-forest global address list (GAL), ensure that you use the Microsoft Identity Manager 2016 SP1 and use the following code in the link to synchronize the source and target mailbox user.
If you have created the target mailbox user by using an Active Directory tool, run the Update-Recipient cmdlet to generate the LegacyExchangeDN. The following link outlines the procedure to create the target user by using PowerShell script.

Steps to enable Exchange Cross-forest Migration
- Step 1: Download and install EdbMails Exchange migration software
  - Download and install the EdbMails application on Windows operating system.
    See a detailed list of EdbMails system requirements for cross forest Exchange migration.
  - Launch the EdbMails application on your computer.
  - Enter your registered email ID and password, then click ‘Login’. If you don’t have an account yet, choose ‘Start Your Free Trial’ to continue with the trial version.
    Note: The trial version includes all core features and allows migration of up to 30 items per folder across mailboxes. For unlimited migration, purchase an Exchange Migration license from the EdbMails website.
    Click here to view Exchange Migration pricing details.
    After completing the purchase, close and reopen the application. Then sign in again using the same email ID and password used during the purchase to activate the license successfully.
  - Select ‘Live Exchange Migration’ option.
  - Select 'Live Exchange to Live Exchange Migration' option.
  - Keep the existing job name or choose ‘New Job’ if you prefer to assign a different name.
- Step 2: Connect to the source Exchange server
  - To establish a new connection to the source Exchange server, click on ‘Add New Connection’. If you have an existing connection, simply select it from the list and click ‘Connect to Existing’ to continue.
  - Select the required connection options and click the ‘Next’ button.
    Different options to connect to Exchange server in EdbMails.
  - Enter the source Exchange server details such as IP address (Domain name), Exchange version, Username and password.
  - Then click the ‘Login’ button to continue.
  - After signing in to your source Exchange server, select a method to load the mailboxes. EdbMails automatically loads the mailboxes by default. However, due to Microsoft API limitations, the application may display only up to 100 mailboxes. If your environment contains more than 100 mailboxes, use the ‘Load Mailboxes using .CSV file’ option to load the complete list.
  - Select ‘Load Mailboxes Automatically’ and click ‘Next’ to proceed.
- Step 3: Select the source Exchange mailboxes
  - Select the mailboxes/folders from the source Exchange server that you intend to transfer to the target server.
  - Click the ‘Next’ button.
- Step 4: connect to the target Exchange server
  - To connect to the target Exchange server, click ‘Add New Connection’ to create a new connection. If a connection is already available, select it from the list and click ‘Connect to Existing’ to proceed.
  - Choose the required options to connect to your target Exchange server and click the ‘Next’ button.
  - Enter the target Exchange server details , and then click the ‘Login’ button to proceed.
  - Select one of the methods to load the target Exchange server mailboxes.
- Step 5: Map the mailboxes between the source and the target servers
  - Select the required mapping option.
  - If EdbMails is installed on your target Exchange server, you can choose to let it automatically create the mailboxes on the target server.
    Learn more about automatic mailbox creation.
  - EdbMails automatically maps mailboxes between the source and target Exchange servers, making it especially helpful for migrating large numbers of mailboxes. This feature minimizes manual work.
- Step 6: Start Exchange cross forest migration
  - After completing the mailbox mapping, click the ‘Start Migration’ button to initiate the migration process.
  - The cross-forest migration process will now begin. You can monitor the ongoing activity through the progress bar displayed in the application. After the migration is successfully completed, EdbMails shows a confirmation message. Click the ‘View Logs’ option to review the detailed migration report.
Exchange Cross forest Post Migration Tasks
- Step 1: Update the MX records to point to the new Exchange server
  To receive messages on the target Exchange server, update the MX records to route email to the new server. Additionally, configure the Autodiscover record so that Outlook can connect to the migrated mailboxes.
- Step 2: Create a new Outlook profile for users in the new domain
  Configure the Outlook profile for each user in your domain if Outlook has problems connecting to the new Exchange server.
- Step 3: Decommission and uninstall the source Exchange server
  After the migration to the target Exchange server is complete, decommission or uninstall the source server, depending on which Exchange server you used as the source.
  Steps to decommission Exchange server 2010
  Steps to decommission Exchange server 2013
Troubleshooting Guide for Exchange Cross-domain Migration
For assistance with migration errors, refer to the Exchange migration troubleshooting guide for a range of potential solutions. Additionally, for more insights into EdbMails Exchange migration, you may refer to the frequently asked questions (FAQs).

Benefits of EdbMails for Exchange Cross-forest Migration

Support for all Exchange Server Versions: EdbMails supports seamless migration from Exchange 2003, 2007, 2010, and 2013 to both Exchange 2016 and 2019.
Cross-forest Migration Capabilities: The software effectively manages cross-forest domain migration without encountering coexistence issues.
Incremental Migration: Incremental migration is designed to prevent the migration of duplicate items during subsequent operations.
Granular Brick-level Migration: With the granular brick-level migration feature, users can precisely select individual mailboxes and specific items for migration.
Public Folder Migration: EdbMails support for Exchange public folders and shared mailbox migration.
Support for all Migration Types: EdbMails Exchange migration software accommodates a variety of migration types, such as cutover, staged, and hybrid migrations.
User-friendly Interface: EdbMails features an intuitive interface that simplifies the navigation process for performing migration operations, requiring no technical expertise.

Frequently Asked Questions (FAQ)

Can I migrate shared and archive mailboxes across forests?
Yes. EdbMails fully provides migrating primary, shared, and archive mailboxes between Exchange servers across forests. The tool ensures complete data consistency and supports incremental migration for these mailbox types.
Do I need coexistence or trust setup between forests?
No. EdbMails does not require coexistence configurations or trust relationships between source and target forests. It allows direct mailbox migration using secure EWS (Exchange Web Services) connections, simplifying complex cross-forest scenarios.