Our experience migrating from Exchange Server to Microsoft 365

We recently performed a migration from an on-premises Exchange Server to Microsoft 365. Our goal was to transfer mailbox data while minimizing disruption to users.

Before starting, we reviewed the source mailboxes, Microsoft 365 accounts, permissions, network availability and mailbox mapping. We then migrated a few test mailboxes to confirm the connection and verify emails, calendars, contacts and folder structures.

For this migration, we used EdbMails Exchange Migration to connect the source and destination environments, map mailboxes and perform the migration in stages.

Most historical data was transferred during the initial migration while users continued working. Before the final cutover, we ran an incremental migration to transfer newly received and modified items.

After migration, we checked:

• Emails, folders, calendars and contacts
• Recent and sent messages
• Archive and shared mailboxes
• Item counts and migration logs
• Mail flow after the DNS changes

Overall, the staged approach made the migration easier to manage and reduced the amount of work required during the final cutover.

Our main lessons were:

• Always begin with a pilot migration.
• Verify permissions and mailbox mapping early.
• Run an incremental migration before cutover.
• Validate the migrated data before retiring the source server.

The migration was completed successfully, and the structured approach helped us maintain data integrity while keeping disruption to users to a minimum.