Moving business email is not just copying messages into Outlook. Your team also depends on calendars, shared addresses, files, phones and applications that send email. A useful migration plan identifies those dependencies before anyone changes where new mail arrives.
This checklist is for businesses using Gmail through Google Workspace with their own domain. Personal @gmail.com accounts need a different assessment. Microsoft 365 is the subscription platform. Exchange Online hosts the business mailboxes, while Outlook is one way staff access them.
1. Decide what is moving
Start with an inventory, not a migration date. Record:
- Every user mailbox, its size and any archives that must be preserved.
- Addresses such as sales@ and billing@, including aliases, Google Groups, forwarding and delegated access.
- Personal and shared calendars, meeting rooms, recurring meetings and important contacts.
- Google Drive files, shared drives, ownership and external sharing.
- Phones, Outlook installations, scanners, website forms and business applications that send mail.
- Retention requirements, legal holds and records that must remain available.
Assign an owner to each item. A Google Group and a Microsoft shared mailbox are not automatically interchangeable. Decide how each shared address should work in the destination and who should have access.
2. Separate email migration from file migration
Microsoft’s native Google Workspace mailbox migration through the Exchange admin center supports email, rules, calendars and contacts, subject to documented limitations. It does not migrate Google Drive files as part of that mailbox migration.
Drive content needs its own plan. Microsoft’s Migration Manager supports copying eligible Google Drive content to OneDrive and SharePoint. Decide where personal work and team-owned information belong before copying them.
Do not assume existing sharing and file history will carry over exactly. Review migration settings, identity mappings, destination permissions, supported file types and version-history options.
In Microsoft’s Migration Manager, file-level permission migration is off by default, so files inherit the destination folder’s permissions unless file-level migration is enabled. External sharing links are not recreated, and content is not automatically shared with external collaborators. Plan any approved destination sharing separately. By default, only the most recent file version is copied. Retaining older versions requires the appropriate settings and validation.
Test important Google Docs, Sheets and Slides after conversion. Check that intended users can open files and that people without permission cannot.
3. Identify exceptions before changing mail delivery
For Microsoft’s native Google Workspace mailbox migration, documented exclusions include:
- Shared calendars.
- Meeting-room bookings.
- Calendar event colors.
- Vacation and automatic-reply settings.
Migrated mailbox rules remain turned off by default and should be reviewed before being enabled.
These limitations are specific to the selected migration method. Another migration product may behave differently. Ask your provider to identify what the selected tool transfers, what it skips and how exceptions will be handled.
Build an exception list for shared calendars, delegates, oversized messages, archives and applications. If a critical item needs to be recreated or preserved another way, make that decision before cutover, the point when new mail starts arriving in Microsoft 365.
4. Prepare access, licensing and security
Confirm that the business controls its domain and can authorize the required administrative changes. Prepare destination accounts and a licensing plan appropriate to the selected migration method. Check mailbox capacity and whether staff need desktop Office applications or additional security features.
Use appropriately scoped administrator roles, protect administrative accounts and treat migration permissions and service-account credentials as sensitive. Plan how temporary migration access will be removed when validation is complete.
Include multifactor authentication, account recovery, email authentication and approved application senders in the destination review.
Microsoft warns that its native Google Workspace mailbox migration does not account for messaging records management (MRM) or archival policies. Messages deleted or moved to archive by those policies can be flagged as missing during migration verification. Review the effect on retention requirements and legal holds with the responsible records or compliance owner before changing any policy. Do not remove a legal hold or change a retention obligation simply to make a migration easier.
5. Test representative users and workflows
Ask the migration provider to explain how representative users and important business workflows will be tested before the final mail-routing change.
Choose users based on how they actually work, not only the simplest mailboxes. Include someone who uses a shared address or delegated calendar and someone who relies on mobile email.
Testing should cover:
- Sending and receiving messages inside and outside the business.
- Searching older messages and opening attachments.
- Calendar invitations, recurring meetings and contacts.
- Shared mailbox or group access.
- Phone and desktop sign-in.
- Scanners, website forms and applications that send email.
Record failed and skipped items as well as successful copies. For Microsoft Migration Manager Drive tasks, a Completed status does not guarantee that every item was copied. Review the migration summary and detailed reports. Also check for unorganized or orphaned Google files, which are not scanned, migrated or included in those reports.
For files, review the available detailed reports and check business-critical documents with their owners. Confirm that permissions, external sharing requirements and required version history are correct at the destination.
6. Agree on cutover and recovery responsibilities
The migration plan should identify who changes mail routing, who authorizes the change and how employees will receive instructions if email is unavailable.
Explain where staff should work during any overlap so information does not continue changing in two places without a plan.
Allow for synchronization, service limits and exceptions. Mailbox size alone cannot determine a reliable completion date. No migration should be represented as guaranteeing zero downtime or zero data loss.
Define the conditions for pausing or reversing the change. A rollback is not simply changing a mail-routing record back. Messages may already have arrived in both systems. The recovery plan should explain how those messages and any other changes will be reconciled.
Identify who is responsible for recovery decisions, source-system access and restoring access to business-critical information.
7. Validate before retiring Google Workspace
Keep source access available until the agreed validation checks are complete.
Have mailbox and file owners verify the information they need. Resolve or document outstanding exceptions and review the available migration logs and reports.
Check:
- New mail delivery and shared addresses.
- Calendar access and important recurring meetings.
- Application and scanner email delivery.
- File permissions and access to business-critical documents.
- Required retention and backup arrangements.
- Outstanding migration errors and excluded content.
Before canceling Google Workspace, review remaining Drive content, Google sign-ins used by other services, records under retention and subscription commitments.
Canceling email service should not accidentally remove access to something the business still needs.
What to ask before approving a migration proposal
- Which accounts, data and applications are included, and what is excluded?
- How will shared addresses, calendars, file permissions and retained records be handled?
- Which users and business workflows will be tested before cutover?
- What should staff expect at cutover, and who owns recovery decisions?
- What migration evidence and validation results will be available before retiring the source service?
- How will external sharing, older file versions and unsupported content be handled?
- Who is responsible for keeping source access available until outstanding exceptions are resolved?
Planning a move?
Considering a move between Google Workspace and Microsoft 365? Tell us about your current setup so we can determine the scope and support required. You can also explore our cloud and Microsoft 365 services.
The starting point is a clear scope, not an assumption that every business needs the same migration.