Select the mail migration strategy for moving your mail data to the cloud


Microsoft 365 provides multiple ways of migrating mail, calendar, and contact information to the cloud. An organization should select the method that best fits its current environment, its migration strategy, and its network configuration. This unit introduces the available migration strategies. Upcoming units in this module analyze the performance considerations of each methodology and the network issues that must be considered when creating a mail migration plan.

There are five migration strategies an organization can choose from to move its data:

  • Internet Message Access Protocol (IMAP) Migration. An organization can use the Exchange Administration Center or the Exchange Management Shell to migrate the contents of its users' mailboxes from an IMAP messaging system to their Microsoft 365 mailboxes. This process also includes migrating the users' mailboxes from other hosted email services, such as Gmail or Yahoo Mail.
  • Cutover migration. A cutover migration migrates all on-premises mailboxes to Microsoft 365 over a few days. A cutover migration should be used if an organization plans to move its entire email organization to Microsoft 365 and manage user accounts in Microsoft 365. A maximum of 2,000 mailboxes can be migrated from an on-premises Exchange organization to Microsoft 365 using a cutover migration. The recommended number or mailboxes, however, is 150. Performance suffers once the number of mailboxes exceeds that amount. The mail contacts and distribution groups in an on-premises Exchange organization are also migrated.
  • Staged migration. A staged migration is similar to a cutover migration in that it ultimately enables an organization to migrate all its mailboxes to Microsoft 365. However, while a cutover migration takes place over a couple of days, a staged migration migrates batches of on-premises mailboxes to Microsoft 365 over the course of a few weeks or months.
  • Hybrid deployment. A hybrid deployment enables organizations to extend the feature-rich experience and administrative control they have with their existing on-premises Exchange organization to the cloud. A hybrid deployment provides the seamless look and feel of a single Exchange organization between Microsoft 365 and an on-premises Exchange Server 2013 or Microsoft Exchange Server 2010. A hybrid deployment can also serve as an intermediate step to moving completely to a Microsoft 365 organization.
  • Third-party migration. There are many tools available from third-parties. They use distinctive protocols and approaches to conduct email migrations from email platforms like IBM Lotus Notes and Novell GroupWise.

Knowledge check

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You're the Enterprise Administrator for Tailspin Toys, Inc. As you plan your Microsoft 365 deployment, you want to select the most appropriate strategy for Tailspin Toys when migrating mail, calendar, and contact information to the cloud. You want to move your entire email organization (3000 mailboxes) to Microsoft 365 and manage user accounts in Microsoft 365. You realize it may take more than a few days to migrate batches of on-premises mailboxes to Microsoft 365. In fact, it may take a few weeks or months. Which migration strategy should you employ to meet these business requirements?