This guide is prepared for users who want to try a manual way to migrate Exchange mailboxes to Office 365. We are going to discuss here the cut-over migration in detail. Let us see the situations where this migration can be performed.

  • For migrations from Exchange Server 2013, 2010, 2007 and 2003.
  • For migrating up to 2000 mailboxes (most ideal for migrating up to 150 mailboxes).

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Preparation for Cut-over Migration

Some important preparations must be done in the current Exchange environment for manual migration of Exchange to Office 365.

  1. Disable directory synchronization by running following command in the Office 365 PowerShell (before this, you need to install Azure AD module to connect to Office 365 organization).
  2. Set-MsolDirSyncEnabled -EnableDirSync $false
  3. Configure Outlook Anywhere on on-premises Exchange Server
  4. For Exchange 2013, Outlook Anywhere is automatically configured. For other Exchange versions, you need to enable it using Exchange Management Console or Exchange Management Shell. For ex-

    Enable-OutlookAnywhere -Server ‘enter name‘ -ExternalHostname ‘enter name‘ -DefaultAuthenticationMethod ‘Basic’ -SSLOffloading $false
  5. Add Outlook Anywhere and Autodiscover services to SSL certificate issued by a trusted Certificate Authority.
  6. For adding certificate, you need a 3-step process – Create a certificate request, submit a request to CA (Certificate Authority) and then Import the certificate.

  7. Assign permissions
  8. Check and assign the required permissions (Full Access permissions on each on-premise mailbox or Receive As permission on the on-premises database) for the user account that is performing the migration. To set these permissions, visit https://support.office.com/en-us/article/assign-exchange-permissions-to-migrate-mailboxes-to-office-365-eb39cfa7-7c76-4403-a2f5-403354ebb7ae

  9. Turn off Unified Messaging before the migration
  10. For this, go to Exchange Admin Center>recipients>mailboxes. Select the requirement mailboxes, click Disable option under Unified Messaging on the right-most side, if the status is Enabled.

  11. Create an empty mail-enabled security group in Office 365
  12. This Office 365 migration method moves mailboxes, mail users, mail contacts, and mail-enabled groups only. It does not migrate security groups. So, you need to create an empty security group. You can do it easily from the Office 365 admin center.

    Also, you need to delete the on-premise Active Directory objects like mailboxes assigned as delegate or manager to an object being migrated to Office 365.

    All these pre-requirements are mandatory before performing the cut-over migration. It avoids the risks in Exchange On-premises to Office 365 migration.

The first article of this articles provides a complete description of pre-requirements for cut-over migration. After meeting all the requirements for cut-over migration, the actual process of migrating Exchange on-premises mailboxes to Office 365 is explained in our next article (part 2) of the series.