Migration Methods Overview
Understanding the Concept
Exchange Online supports several migration methods: cutover migration (all mailboxes at once), staged migration (batches from Exchange 2003/2007), hybrid migration (coexistence with on-premises), and IMAP migration (from third-party systems).
Cutover migration is suitable for small organizations (under 2000 mailboxes) moving entirely from on-premises Exchange. All mailboxes, contacts, and distribution groups are migrated in a single batch.
Hybrid migration provides the most seamless experience with shared namespace, free/busy lookups, and mailbox moves. It requires Hybrid Configuration Wizard (HCW) setup and Azure AD Connect for directory synchronization.
Key Points
Migration Decision Flow
Assess Source
Identify current email platform
Choose Method
Select migration type based on requirements
Prepare
Configure prerequisites and test
Execute
Migrate mailboxes and validate
Why This Matters
Choosing the wrong migration method can lead to extended downtime, data loss, and user frustration. Understanding each method's requirements and limitations is critical for successful Exchange Online adoption.