Understanding Office 365 Cutover Migration
What is Cutover Migration?
Office 365 provides multiple migration option to the customers based on source messaging systems. We can either use Office 365 based native migration tools or we can leverage 3rd party toolset like BitTitan, Quest and many more tools to migrate mailbox data from source messaging system to office 365.
Cutover Migration is defined as “The process of migrating on premises Exchange mailboxes to office 365 in a single migration batch. Migration batch migrate on premises mailboxes, distribution lists and Mail Contacts to Office 365”
Office 365 provides customer with a native cutover migration tool that can migrate user’s email, contacts, calendar and tasks from Exchange 2003, 2007 and 2010 to Office 365 without requiring additional licenses for data migration.
The WindowsEmailAddress attribute is used as the primary key for the cutover migration and changing the WindowsEmailAddress attribute during a cutover migration isn’t recommended.
Outlook Anywhere must be functional to use Native Office 365 Cutover Migration tool.
How Cutover Migration Works?
Thanks to Microsoft for below Diagram that shows how a cutover migration works.
What you need to plan about Cutover Migration?
Before you start migrating your users using native cutover migration tool, below is the information that you must be aware of as an administrator.
- Exchange online connects with on prem exchange server using outlook anywhere. Outlook Anywhere must be working properly if you want to leverage Native Cutover tool.
- Based on Address book, exchange online will spun up user mailboxes, Distribution List and Mail Contacts in Exchange online and start initial synchronization process. Hide the user mailbox, Distribution list and Mail Contact in address book if you do not want to synchronize to Office 365.
- Native Cutover Migration tool will not migrate Dynamic Distribution Groups and Public Folders to Office 365.
- Cutover Migration tool will migrate Shared Mailboxes as user mailbox in Office 365. After the cutover you need to manually convert those mailboxes to Shared Mailbox in Office 365.
- Distribution groups will be migrated with Default permissions in Office 365. By default office 365 Distribution Groups aren’t allowed to receive external emails. If you have any Distribution group that receive external email then modify the settings after the migration.
- Cutover Migration support up to 2000 mailboxes to be migrated. If you’ve more then 2000 mailboxes in Exchange then you need to choose a different migration option. It’s recommended to use Cutover Migration for up to 150 mailboxes.
- All users have to reconfigure Outlook and Active Sync clients after the public DNS cutover to Office 365.
- Directory Synchronization isn’t supported with Native Cutover tool. If you want to leverage Directory Sync tool then you can deploy the tool after the cutover migration.
- Native Cutover tool will perform delta synchronization after every 24 Hrs once the initial sync is completed for up to 90 days. Migration batch will be automatically stopped after 90 days.
- Administrator needs to complete the migration within 90 days. Once the batch is stopped after 90 days. It will be automatically deleted within 30 days.
- Your SMTP domain must be added in Exchange online as Accepted Domain. Once the domain ownership is verified in Office 365 it will be automatically added to Accepted domains.
- You must communicate your end users with the transition to Office 365.
For more information please read following Microsoft articles.