Elephants1. Define scope
- Record the source, destination, domains and selected users.
- Separate mail from contacts, calendars, rules, delegates and archives.
- Inventory mailbox sizes, quotas and retention constraints.
2. Validate access and destinations
- Confirm the source authentication method and API or IMAP availability.
- Create and license every destination mailbox.
- Verify application permissions, quotas and tenant restrictions.
3. Run a representative pilot
Select small, large and operationally important mailboxes. Review folder behavior, item dates, throughput, throttling and exceptions before increasing batch size.
4. Plan cutover
Document user communications, DNS responsibility, coexistence, the final latest-changes pass, support coverage and the decision owner who accepts the result.
5. Reconcile outcomes
Compare expected and processed scope, investigate skipped and failed items, rerun eligible exceptions and retain the approved completion report.