- December 10, 2019 at 8:53 am #156493AdrianG001Participant
As part of an Office 365 deployment, you can migrate the contents of user mailboxes from a source email system to Office 365. When you do this all at one time, it’s called a cutover migration. Choosing a cutover migration is suggested when:
Your current on-premises Exchange organization is Microsoft Exchange Server 2003 or later.
Your on-premises Exchange organization has fewer than 2,000 mailboxes.
Plan for migration
Setting up an email cutover migration to Office 365 requires careful planning. Before you begin, here are a few things to consider:
You can move your entire email organization to Office 365 over a few days and manage user accounts in Office 365.
A maximum of 2,000 mailboxes can be migrated to Office 365 by using a cutover Exchange migration. However, it is recommended that you only migrate 150 mailboxes.
The primary domain name used for your on-premises Exchange organization must be an accepted as a domain owned by you in your Office 365 organization.
After the Exchange to Office migration is complete, each user who has an on-premises Exchange mailbox also will be a new user in Office 365. But you’ll still have to assign licenses to users whose mailboxes are migrated.
How does cutover migration work?
The main steps you perform for a cutover migration are shown in the following illustration.
The administrator communicates upcoming changes to users and verifies domain ownership with the domain registrar.
The administrator prepares the servers for a cutover migration and creates empty mail-enabled security groups in Office 365.
The administrator connects Office 365 to the on-premises email system (this is called creating a migration endpoint).
The administrator migrates the mailboxes and then verifies the migration.
Grant Office 365 licenses to your users.
The administrator configures the domain to begin routing email directly to Office 365.
The administrator verifies that routing has changed, and then deletes the cutover migration batch.
The administrator completes post-migration tasks in Office 365 (assigns licenses to users and creates an Autodiscover Domain Name System (DNS) record), and optionally decommissions the on-premises Exchange servers.
The administrator sends a welcome letter to users to tell them about Office 365 and to describe how to sign in to their new mailboxe.
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