Exchange to Office 365 migration guide

1. Assign the Organization Management role group to the admin user on both the source and the target. It is an elevated permission that is required to migrate Public folders.
2. Install cumulative updates (CU) on the source Exchange server.
   1. Install for Exchange server 2013
   2. Install for Exchange server 2016
   3. Install for Exchange server 2019
3. Set the impersonation rights for the admin account in Office 365 to migrate mailboxes on behalf of other users in your organization.Verify if the source and target admin account in general has the following management roles assigned:
   1. ApplicationImpersonation
   2. View-Only Configuration
   3. View-Only Recipients
   4. Public Folders
   5. User management administrator/Global administrator
4. Check if the Global admin account that has been assigned management roles has a valid and non-hidden mailbox on the source and target server.
5. Ensure that you meet the network and bandwidth requirements for the migration. See Network and migration planning for Office 365.
6. Decide the migration path you want to migrate depending on your environment.

   Current environment and requirement	Migration approach	How does the migration take place?
   You want to perform a complete Office 365 migration in a single event and in a limited time frame.	Cutover migration	In this approach, you set up your target Office 365 tenant and migrate everything in a single sitting. Suited for large mailbox migration
   You want to perform the migration in phases	Staged migration	In this approach, you migrate your mailboxes and mail data in stages and transfer the most recent/required data first followed by the others.
   You have an on-premises Exchange server that coexists with Office 365 cloud	Hybrid migration	In this approach, you migrate within the Hybrid environment to Office 365 or from a Hybrid environment to an independent Office 365 tenant

    See performance factors and best practices for Office 365 migration.

7. Prepare your target Office 365 tenant. See Tenant roadmap for Microsoft 365.
8. Before migrating to the target Office 365 tenant, ensure that you create mailboxes for your users in your organization and assign suitable licenses to them.
   •  Add users and assign licenses to Office 365 users
   •  Add several users at the same time to Office 365
   •  Assign Microsoft 365 licenses to user accounts
9. If you plan to migrate the source Public folders to Public folders on Office 365, ensure that you create and configure the Public folder mailboxes on the target server.

    Create Office 365 Public folder and assign mailbox user

10. If you have a custom email domain from your source to which you want to receive emails after the migration, you must add and verify the domain on Office 365.

     Steps to add a custom domain to Office 365 and steps to add DNS records to connect your domain.

11. If you are using Active Directory Federation Services, you must configure a new domain on the target tenant for AD FS.
12. Configure Office 365 to send and receive large messages.

     Follow the steps to increase the message size on Office 365 to 150MB.

There are three methods to migrate Exchange to Office 365

Steps to migrate Exchange server to Exchange online

1. Cutover Exchange migration
2. Staged migration
3. Hybrid Exchange migration to Office 365

See the troubleshooting solutions for Office 365 and Exchange migration. For more information related to EdbMails Exchange migration, see frequently asked questions.