A Google Workspace to Microsoft 365 migration affects email, calendars, contacts, files, shared drives, identity and, frankly, people's daily habits. The technical move is only part of the project. The bigger challenge is making sure users understand where their data has gone and how work should happen afterwards. Ignore that and you will have a technically perfect migration that everyone hates.
Here is the checklist we work through. If you want a hand, our Google Workspace to Microsoft 365 migration service covers the lot.
1. Define scope before choosing tools
People love to argue about migration tools. It is almost never the important decision. Scope first, tools second.
| Check | Why it matters | Evidence to collect | Owner/status |
|---|---|---|---|
| Gmail mailboxes | Defines email migration volume and batch strategy. | Mailbox list, aliases, forwarding, mailbox size. | |
| Calendars and contacts | Google calendar behaviour does not map perfectly to Outlook in every scenario. | Shared calendars, room calendars, recurring meetings, contacts. | |
| My Drive | Usually maps to OneDrive, but personal/business boundaries need review. | User drive sizes, shared files, ownership patterns. | |
| Shared Drives | Usually maps to SharePoint sites or Teams-backed document libraries. | Shared Drive list, owners, permissions, size, active usage. | |
| Google Groups | Must be mapped to M365 Groups, distribution lists, shared mailboxes or Teams depending on use. | Group inventory, members, posting permissions. |
2. Map the destination architecture
The most important decision is not which button starts the migration. It is where Google content should land in Microsoft 365. If the destination architecture is poor, the migration simply moves the old mess into a new platform. We see this all the time: a company lifts every Shared Drive into one giant SharePoint site and then wonders why nobody can find anything.
| Google source | Typical Microsoft 365 destination | Design question |
|---|---|---|
| Gmail | Exchange Online | Will users keep aliases, delegates and forwarding rules? |
| Google My Drive | OneDrive for Business | Is this genuinely personal work data or should some content become team-owned? |
| Google Shared Drives | SharePoint Online or Teams | Which department, project or function owns the content? |
| Google Groups | Distribution List, M365 Group, Shared Mailbox or Team | Is the group for email, security, collaboration or file access? |
| Google Sites | SharePoint communication site or manual rebuild | Is the site still needed, and is content current? |
3. Identity, domains and licensing
- Verify Microsoft 365 tenant domains before migration.
- Create or synchronise users before mailbox migration.
- Confirm primary SMTP addresses and aliases.
- Check conflicting cloud-only users and duplicate proxy addresses.
- Assign licences early enough for mailbox and OneDrive provisioning.
- Prepare admin accounts with appropriate roles and MFA.
4. Gmail migration planning
| Check | Why it matters | Evidence to collect | Owner/status |
|---|---|---|---|
| Mailbox batches | Controls risk and support load. | Batch list by department, VIP and mailbox size. | |
| Rules and filters | Some rules may migrate disabled or need user verification. | User communication and post-migration support guide. | |
| Delegation | Shared access patterns may need reconfiguration. | Delegated mailbox access list. | |
| Large messages | Oversized messages can fail depending on limits. | Migration error reports and exception plan. | |
| DNS cutover | MX, SPF, DKIM and Autodiscover must be changed deliberately. | DNS plan with TTL and rollback notes. |
Microsoft have a specific walkthrough for this in their Google Workspace migration guide, which is worth reading alongside this checklist.
5. Drive and Shared Drive preparation
- Scan Google Drive content before migration and review scan reports.
- Identify files with unsupported names, excessive path lengths or permission issues.
- Clean up redundant Shared Drives before moving data.
- Map Google permissions to Microsoft 365 users and groups.
- Decide how externally shared content should be handled.
- Pilot at least one Shared Drive migration before bulk migration.
Practical warning: Shared Drives often reveal poor ownership. Do not migrate them blindly. Use the migration as a chance to decide which content belongs in a SharePoint site, which belongs in Teams and which should be archived. This is exactly the sort of design work our SharePoint consultants do every week.
Microsoft's Migration Manager for Google Workspace can handle a good chunk of the file side, but it will not fix a broken structure for you.
6. Communications and adoption
This is the bit technical teams skip, and it is the bit users remember. Do not skip it.
- Tell users what is changing and when.
- Explain Gmail to Outlook differences before go-live.
- Provide quick-start guides for Outlook, Teams, OneDrive and SharePoint.
- Make clear where files should live after migration.
- Schedule floorwalking or drop-in support for the first working day.
- Track recurring issues and update guidance quickly.
7. Post-migration validation
| Check | Why it matters | Evidence to collect | Owner/status |
|---|---|---|---|
| Mail delivery | Check internal, external, inbound and outbound mail. | Test emails and message trace samples. | |
| Calendar behaviour | Recurring meetings and shared calendars can cause user-visible issues. | Pilot test cases and user feedback. | |
| OneDrive data | Users need confidence that personal work files arrived. | Sample validation and migration reports. | |
| SharePoint permissions | Incorrect permissions create either access issues or exposure. | Access tests for selected departments. | |
| Google tenant shutdown | Old mail flow and file sharing should not continue indefinitely. | Decommission and retention plan. |
Book a Migration Readiness Assessment
Moving from Google Workspace to Microsoft 365? We can assess your Workspace estate, design the migration approach and support the move with minimal disruption.
Book a Migration Readiness Assessment