This content is part of the Essential Guide: The essential Office 365 migration guide

Explaining cutover vs. staged Office 365 migrations

Various options exist for companies planning Office 365 migrations. Cutover and staged migrations are possibilities, but what exactly do they entail?

My company is planning a move to Microsoft Office 365. I've read about cutover and staged migrations and am curious...

where each is needed and what the key differences are. Can you please explain?

Cutover Office 365 migrations use either IMAP or RPC over HTTP to extract email messages from your on-premises Exchange servers and copy them to the cloud. Once the messages have been moved, the DNS records are changed to point to the hosted Exchange servers, in order for users to begin using Exchange in the cloud.

Staged Office 365 migrations are similar to cutover migrations, but the key difference is that users are migrated in batches. Therefore, the assumption is that there will be a coexistence period between the hosted Exchange Server deployment and the on-premises deployment.

There are various considerations to take into account when it comes to choosing a migration type, but one of the most important is mailbox data volume. It may prove impossible to migrate large numbers of mailboxes or vast quantities of mailbox data within an allotted period of time. In these types of situations, a staged migration is more effective than a cutover migration.

You also have the option to perform a hybrid coexistence migration. Such a migration is complex, but is ideally suited for large organizations that require an extended coexistence period. In this type of migration, you must establish Active Directory synchronization and single sign-on between the on-premises and hosted Exchange deployments. The advantage here is that a hybrid coexistence migration lets you migrate mailboxes at your leisure, using native Exchange Server tools.

About the author:
Brien Posey is a ten-time Microsoft MVP with two decades of IT experience. Before becoming a freelance technical writer, Brien worked as a chief information officer at a national chain of hospitals and health care facilities. He has also served as a network administrator for some of the nation's largest insurance companies and for the Department of Defense at Fort Knox.

Dig Deeper on Exchange Server setup and troubleshooting