The administrator prepares the servers for a cutover migration and creates empty mail-enabled security groups in Microsoft 365 or Office 365. The administrator communicates upcoming changes to users and verifies domain ownership with the domain registrar. The main steps you perform for a cutover migration are shown in the following illustration. Potential delay in email routing: Email sent to on-premises users whose mailboxes were migrated to Microsoft 365 or Office 365 are routed to their on-premises Exchange mailboxes until the MX record is changed. After updates are made, users can send email from Outlook 2013, Outlook 2010, or Outlook 2007.
Users with permission to install applications can update and set up their own desktops. These actions allow users to use local user credentials to sign in to Microsoft 365 or Office 365 from desktop applications. When migrating from Exchange 2003, TCP port 6001, 60 need to be open on the Exchange 2003 side.Īfter your on-premises and Microsoft 365 or Office 365 organizations are set up for a cutover migration, post-setup tasks could impact your users.Īdministrators or users must configure desktop computers: Make sure that desktop computers are updated and set up for use with Microsoft 365 or Office 365. The primary domain name used for your on-premises Exchange organization must be an accepted as a domain owned by you in your Microsoft 365 or Office 365 organization.Īfter the migration is complete, each user who has an on-premises Exchange mailbox also will be a new user in Microsoft 365 or Office 365, but you must still assign licenses to users whose mailboxes are migrated. However, it is recommended that you only migrate 150 mailboxes. You can move your entire email organization to Microsoft 365 or Office 365 over a few days and manage user accounts in Microsoft 365 or Office 365.Ī maximum of 2,000 mailboxes can be migrated to Microsoft 365 or Office 365 by using a cutover Exchange migration. Before you begin, here are a few things to consider: Setting up an email cutover migration to Microsoft 365 or Office 365 requires careful planning. Even though cutover migration supports moving up to 2000 mailboxes, due to length of time it takes to create and migrate 2000 users, it is more reasonable to migrate 150 users or fewer.