A situation where two organizations, using separate Microsoft 365 account, are merging for collaboration will require a consolidated Microsoft 365 account for email communication. In this case, the mailboxes from one Microsoft 365 account need to be migrated to another. Since the migration will be a cross-domain migration, the manual process will be difficult and time consuming. To avoid this, you can migrate mailbox data from one Microsoft 365 account to another using Stellar Migrator for Exchange.

Steps to Migrate mailboxes from one Office 365 tenant to another using Stellar Migrator for Exchange

Here are the steps to use the software and migrate the mailbox data from one Microsoft 365 tenant to another.

  1. Download and open Stellar Migrator for Exchange. From the Login ribbon, select Login and then enter your login credentials Like User ID and Password. Click on Log in.

    Download and open Stellar Migrator for Exchange. From the Login ribbon, select Login and then enter your login credentials Like User ID and Password. Click on Log in.
     
  2. The Status will change to Connected and you will be able to see the number of available licenses. Click on OK.

    The Status will change to Connected and you will be able to see the number of available licenses. Click on OK.
     
  3. In the job Ribbon, click on New to create a new migration job.

    In the job Ribbon, click on New to create a new migration job.
     
  4. Configure general setting of the job
    1. Enter the Job Name
    2. Select Microsoft 365 as the source server type
    3. Select Microsoft 365 as the destination server type.
    4. Once you have configured the General settings, click on Next.

    Configure general setting of the job
     
  5. Select the check box if you want to upload a CSV file containing mailboxes on the source server mapped to the mailboxes on the destination server. Then, click on the Import button to import the CSV file from your system.
    Note:
    1. If you do not select the check box, you will later get an option to manually map the mailboxes.
    2. You can also download a template that you can use to create the CSV.
     
  6. The next step is to select the type of mailbox that you want to migrate from the source server. In the software you can select:
    • Primary Mailboxes
    • Archive mailboxes
    • Public folders
      You can select all the types or particular types of the mailboxes to migrate. Then Click Next.

      The next step is to select the type of mailbox that you want to migrate from the source server. In the software you can select:
       
  7. In the Connect Source tab, you can use 
    1. Auto registration: With this option, you will be redirected to the Office 365 login window and there you will have to login with the Global admin account credentials. Auto app registration - Source window appears, displaying the registration process. This includes steps such as registering the application in Azure AD, and assigning Microsoft Graph API permissions. When the registration is successful, the check icon next to each step, such as Registering the application in Azure AD, assigning Microsoft Graph API permissions, and granting admin consent for these permissions, will turn green.

    In the Connect Source tab, you can use 

    2.      You can select Manual registration and manually register an application with Azure AD and note the client ID, tenant IDs and client secret value. You then need to enter these values in the respective fields and connect to Microsoft 365.

    2.  You can select Manual registration and manually register an application with Azure AD and note the client ID, tenant IDs and client secret value. You then need to enter these values in the respective fields and connect to Microsoft 365.
     
  8. In the next section, you can see the list of mailboxes that the software found on the source Microsoft 365 tenant. Although, If you did not use a CSV file, you will be able to view up to 100 mailboxes. If you have more than 100 mailboxes, you can click on Load mailboxes using CSV, Upload a CSV file and view all the mailboxes. Once you have viewed the list of source mailboxes, Click on Next.

    In the next section, you can see the list of mailboxes that the software found on the source Microsoft 365 tenant.
     
  9. Next, you need establish a connection with the target server. Similar to the process of connecting to the source server, you can use Auto Registration to connect to the target Office 365. Auto registration: With this option, you will be redirected to the Office 365 login window and there you will have to login with the Global admin account credentials. Auto app registration - Source window appears, displaying the registration process. This includes steps such as registering the application in Azure AD, and assigning Microsoft Graph API permissions. When the registration is successful, the check icon next to each step, such as Registering the application in Azure AD, assigning Microsoft Graph API permissions, and granting admin consent for these permissions, will turn green. Alternatively, Manual Registration will allow you to enter the necessary details.

    Next, you need establish a connection with the target server

  10. When the target is connected, you can see the list of mailboxes that the software found on the target Microsoft 365 server. Although, if you did not use a CSV file for the mailboxes, you will be able to view up to 100 mailboxes. If you have more than 100 mailboxes, you can click on Load mailboxes using CSV, Upload a CSV file and view all the mailboxes. Once you have viewed the list of target mailboxes, Click on Next.

    When the target is connected, you can see the list of mailboxes that the software found on the target Microsoft 365 server.
     
  11. In the next step you will have to map the mailboxes on the source Microsoft 365 server to the mailboxes on the target Microsoft 365 server. If you have uploaded a CSV file, all the mailboxes will be already mapped. Otherwise, the software will map the mailboxes using the mailbox IDs. However, if there is no matching mailbox ID the mailbox will remain unmapped and you will have to map the mailboxes manually. For this:
    1. Click on the ellipsis icon in front of the unmapped mailbox and select a mailbox from the list to map it.
    2. You can also click on the ellipsis icon in front of a mailbox that is mapped and remove or change the mapping.

    The priority section shows you the order in which the software will pick the mailboxes to migrate. You can change this priority from this section. Once you have made all the changes, click Next.

    In the next step you will have to map the mailboxes on the source Microsoft 365 server to the mailboxes on the target Microsoft 365 server.
     
  12. In the next step you can set a date filter to select items for migration based on their date. There are four options available to select items based on dates:
    1. Migrate all items: Select this option to migrate mail items.
    2. Migrate only items older than: Choose this option to migrate only mail items older than the specified date.
    3. Migrate only items not older than: Select this option to migrate mail items that are not older than the specified date.
    4. Migrate only items from: Choose this option to migrate mail items within a specific date range.

    In the next step you can set a date filter to select items for migration based on their date. There are four options available to select items based on dates:
     
  13. Next is the Folder type filter section, here you can include or exclude specific folders from being migrated. By default all, the folders are selected, if you want to exclude a particular folder you can un-check the check box in front of that folder.
    There are two types of folders:
    1. Folders
    2. Special Folders

    Next is the Folder type filter section,
     
  14. Choose the number of mailboxes to migrate simultaneously, with a maximum limit of 10.
    Note: The number of mailboxes that the software can migrate at once depends on the RAM and other configurations of your system.

    Choose the number of mailboxes to migrate simultaneously, with a maximum limit of 10.
     
  15. Review and confirm all configuration settings before proceeding with the migration. If you want to make changes in any section, you can select that section and make the changes. Once you have confirmed all the changes, click on Finish. Your Migration Job will be created successfully.

    Review and confirm all configuration settings before proceeding with the migration.
     
  16. The created job will be displayed on the Job screen. You have to click on Start under the Job ribbon to initiate the migration.

    The created job will be displayed on the Job screen. You have to click on Start under the Job ribbon to initiate the migration.
     
  17. When you start the job, the status of that job turns to green as shown in the image. On the screen, you can see the progress and details of the complete job and you can also see the progress of as single mailbox along with other details.

    When you start the job, the status of that job turns to green as shown in the image
     
  18. At any point you can pause the migration process by using the Pause button under the Job ribbon. In the paused state, the status of the job will turn yellow. To resume the job click on Resume under the Job ribbon.

    At any point you can pause the migration process by using the Pause button under the Job ribbon
     
  19. When you scroll towards the right, in the job progress section, you can see the migration status of the mailboxes. If any mailbox fails to migrate, you can see the reason here; fix it and then re-run the migration. The software supports incremental migration and no duplicate data will be transferred.

    When you scroll towards the right, in the job progress section, you can see the migration status of the mailboxes.
     
  20. Similarly, you can see view the status of items in a particular mailbox. For this, select the mailbox from the Job progress screen and check the details in the mailbox progress section.

    Similarly, you can see view the status of items in a particular mailbox. For this, select the mailbox from the Job progress screen and check the details in the mailbox progress section.
     
  21. At any point, you can generate a Migration report for all the mailboxes or a particular mailbox. By clicking on the save icon. You can save this generated report on your system.

    At any point, you can generate a Migration report for all the mailboxes or a particular mailbox. By clicking on the save icon. You can save this generated report on your system.
     
  22. Once a mailbox is migrated, the Action status for it, changes from Migrate to Don’t Migrate. Additionally, the Migration progress will change to Completed. When the Migration progress of all the mailboxes is changed to Completed, the mailboxes will be migrated.
     
  23. You can then access your Target Microsoft 365 account and check if all the mailboxes are migrated successfully.