Cross-forest migration from Exchange 2013 to 2019/2016

Cross-forest migration involves transferring mailboxes, data, and other resources between different Active Directory forests. This process is typically required when organizations undergo restructuring, mergers, acquisitions, or business consolidations, necessitating the unification of disparate Active Directory environments. Cross-forest migration is essential when two organizations with separate Active Directory forests need to merge their IT infrastructures. This migration helps consolidate resources, improve management, and ensure that all systems operate within a unified environment, enhancing collaboration and efficiency within the organization.

Migrating user mailboxes between different Active Directory forests can be a challenging and time-consuming task, especially when using native migration methods. Cross-forest migrations typically involve running complex PowerShell cmdlets or setting up a trust relationship between the source and target servers. The process becomes even more complicated when upgrading from older Exchange versions to Exchange 2016 or 2019, often requiring a two-step migration.

EdbMails Exchange migration software offers a faster, simpler alternative for cross-forest migration between on-premises Exchange environments. Its intuitive, wizard-driven interface automates much of the process, eliminating many of the manual steps required in native migration approaches.

EdbMails supports migration of mailboxes, public folders, archive mailboxes, and shared mailboxes across different Active Directory forests, ensuring a smooth migration without any coexistence issues. For example, it allows direct migration from Exchange 2010 or 2013 to Exchange 2016 or 2019 with just a few clicks, simplifying the entire process.

The software is optimized for high performance, featuring incremental migration to transfer only new or modified items after the initial migration. This reduces the overall time and effort required while ensuring data integrity during the subsequent migration operations. Additionally, automatic throttling is built in to manage server load efficiently, preventing performance issues during migration.

EdbMails further enhances efficiency by enabling concurrent migration of up to 20 mailboxes at a time, making it ideal for large-scale migrations. Its advanced filter settings provide granular control, allowing you to include or exclude specific data based on parameters such as date range, sender address, recipient address, attachments name, subject, read or unread status of the messages etc. ensuring that only relevant items are migrated.

The following sections provide comprehensive details on the prerequisites for cross-forest Exchange migration, migration steps, and post-migration tasks to ensure a smooth and successful migration operation.

1. 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	Install Cumulative Update 21 (CU21) or later on Exchange 2013 Install Cumulative Update 11 (CU11) or later on Exchange 2016	With EdbMails Exchange migration software, you can migrate to any Exchange server version regardless of the coexistence issue
   Exchange 2016	Possible. Can coexist with Exchange 2013 Can coexist with Exchange 2010	Install Cumulative Update 10 (CU10) or later on Exchange 2013 Install the latest Rollup update for Exchange 2010 Service Pack (SP3)

   • 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.

     1. Network and directory requirement for Exchange 2016
     2. Network and directory requirement for Exchange 2019
     3. Hardware Requirements for Exchange 2016
     4. Hardware Requirements for Exchange 2019
     5. Supported operating systems for Exchange 2016
     6. Supported operating systems for Exchange 2019
   • 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.

     1. Exchange 2019 prerequisites for preparing Active Directory (AD)
     2. Windows Server prerequisites for Exchange 2019
     3. Exchange 2016 prerequisites for preparing Active Directory (AD)
     4. Windows Server prerequisites for Exchange 2016

     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 migration, it's important to ensure that mailboxes are created on the target server. EdbMails automatically creates mailboxes on the target server, streamlining the process for users. However, if you prefer to create mailboxes manually, please refer to the links below for guidance.

        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.

2. EdbMails: Exchange cross forest migration step by step

   • Step 1: Download and install EdbMails Exchange server migration software setup

     • Download and install the EdbMails application on Windows operating systems that have connectivity to both the source and target environments. .Alternatively, you may conduct the migration by installing EdbMails on a non-Exchange server computer.
     • Launch the application and either ‘log in’ or select the ‘Start Your Free Trial’ option to continue.

       

     • Choose the 'Live Exchange Migration' option for cross-forest migration, then move on to the next step to assign the required permissions to the Global administrator account.

       

        Complete list of system requirements for EdbMails Exchange migration.
   • Step 2: Connect to the source Exchange server
     • Select the required connection options
     • If you are using the global admin account to connect to the source Exchange server, ensure to set impersonation rights.

       

        Exchange server connection methods supported by EdbMails

        With EdbMails, you can migrate mailboxes, public folders, and archive mailboxes from the source Exchange to the target server.

     • Enter your source Exchange server details and click the ‘Login’ button

       

     • Once you’ve logged into your source Exchange server, choose the option to load the mailboxes. EdbMails will automatically fetch your Exchange server mailboxes. You can also load mailboxes using a CSV file.

       

   • Step 3: Select the source Exchange mailboxes
     • Select the mailboxes and folders from the source Exchange server that you intend to transfer to the target server.
     • Next, click 'Migrate to Live Exchange' to initiate the connection with the target server.

       

   • Step 4: connect to the target Exchange server
     • Select the required connection option. If you are using a Global admin account to connect to the target Exchange server, ensure to set impersonation rights.
     • Next, click 'Migrate to Live Exchange' to initiate the connection with the target server.

       

     • Enter the target Exchange server details , and then click the ‘Login’ button to proceed.

       

     • Choose the desired option to load your mailboxes.

       

   • Step 5: Map the mailboxes between the source and the target servers
     • Choose the appropriate option for mapping your mailboxes.
     • If EdbMails is installed on your target Exchange server, you can choose to automatically create mailboxes on your target server.
     • Know more about automatic mailbox creation on target Exchange server.

       

     • EdbMails automatically maps the mailboxes and folders from your source server to the target server, eliminating the manual effort.

       

     • Click the ‘Folder and Item Filter’ button to set up your migration preferences. For instance, you can apply a date filter to migrate data only within a specified date range. Additionally, you have the option to exclude both standard and custom folders from the migration process.

       

   • Step 6: Start Exchange cross-forest migration
     • Once you have finished mapping the mailboxes, click the ‘Continue’ button, enter a job name, and proceed. You can monitor the cross forest migration progress in real-time, with the option to pause and resume the operation as needed. Upon completion of the migration, you will receive a confirmation message. Additionally, you can verify the migrated folders and mailbox items through EdbMails' text-based migration report.

       

3. Exchange cross-forest post-migration tasks

   • Step 1: Update the MX records to point to the new Exchange server

     To receive messages on the Exchange server 2019 to 2016, update MX records to enable email to work with the new server you have migrated to. In addition, configure the Autodiscover record to allow Outlook to 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

4. Exchange cross domain migration troubleshooting

   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).

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Additional resources:

• EdbMails Exchange migration
• Exchange to Exchange migration
• Exchange to Office 365 migration
• Exchange 2010 to 2019 migration
• Exchange 2013 to 2019 migration
• Exchange 2016 to 2019 migration
• Exchange 2010 to 2016 migration
• Exchange 2013 to 2016 migration