// overview
The brief
A 35-user professional services business that had been on Google Workspace for six years. They were switching to M365 Business Premium primarily for Intune device management and better integration with their Windows fleet. The migration had to happen over a weekend with no data loss and minimal disruption to staff on Monday morning.
Google Workspace migrations are more complex than moving between Microsoft tenants because the data formats are different. Gmail doesn't map directly to Exchange, Google Drive files aren't native Office format, and calendar/contact data needs specific handling. This writeup covers exactly what was done, in order.
⚠️
Plan for two to three weeks of preparation. The cutover itself is a weekend job, but the preparation work - setting up the M365 tenant, configuring DNS, running test migrations, and training users - takes at least two weeks for a business of this size. Rushing that phase creates the problems.
// phase 1
Tenant setup and pre-migration
Before touching any data, the M365 tenant needs to be fully configured. This is the work that happens two weeks before cutover.
Create user accounts in M365
Create all 35 user accounts in the M365 admin centre. Match UPNs to the primary email addresses users already have in Google. Assign M365 Business Premium licences to all accounts.
Verify the domain in M365
Add the organisation's domain to M365 and complete DNS verification. At this stage, do not change MX records. Mail still flows to Google. The domain verification just proves ownership to Microsoft.
Configure email authentication (SPF, DKIM, DMARC)
Set up SPF and DKIM for Microsoft 365 before cutting over. DMARC can stay in monitoring mode at p=none. This avoids deliverability issues the moment MX records change.
Run pre-migration in BitTitan MigrationWiz
Set up MigrationWiz, connect to Google Workspace with a service account, and run the first pre-migration pass for all mailboxes. This migrates the bulk of historical email while Google is still live, so the final cutover pass is fast.
Convert Google Drive files
Google Docs, Sheets, and Slides are not native Office format. MigrationWiz converts them to .docx/.xlsx/.pptx during migration, but formatting doesn't always survive. Warn users in advance and have a process for flagging broken documents.
// phase 2
Cutover weekend
The cutover itself follows a strict sequence. Any step done out of order creates problems that are difficult to unpick.
| Time | Action | Notes |
|---|
| Friday 17:00 | Send user comms | Email all staff explaining the change, new sign-in details, and what to do Monday morning |
| Friday 18:00 | Run final delta migration | MigrationWiz delta pass picks up any email received after the initial pre-migration |
| Friday 20:00 | Change MX records to Microsoft | TTL should already be set to 300 (5 min). New mail now flows to Exchange Online |
| Saturday 09:00 | Migrate Google Drive to SharePoint | Shared drives become SharePoint document libraries. Personal Drive content goes to OneDrive |
| Saturday 14:00 | Migrate contacts and calendars | Google Calendar events and Contacts export via MigrationWiz to Exchange calendars and Outlook contacts |
| Sunday 10:00 | Device setup and Outlook configuration | Set up Outlook on all devices, confirm mail is flowing correctly, test shared mailboxes |
| Monday 08:00 | Staff arrive | Help desk on standby for the first two hours. Most common issue: MFA setup on first login |
// problems hit
Issues encountered and how they were resolved
Around 8% of Google Docs files failed to convert cleanly to .docx. Most were complex documents with Google-specific formatting. Resolution: provided users with a list of affected files and had them re-export from Google Docs directly in the first week after migration.
Conditional Access required MFA registration on first sign-in. Several staff had not set up the Authenticator app in advance despite the user comms. Resolved by having IT run the MFA registration flow with affected users on Monday morning. Added a Temporary Access Pass process for this in future migrations.
Google Shared Drive permissions don't map directly to SharePoint permissions. MigrationWiz migrates the files but not the folder-level permission structure. SharePoint permissions were set up manually beforehand using the documented permission matrix from the Google Workspace admin console export.
// outcomes
Results
35
Accounts migrated with full mail, calendar, and contacts
0
Emails lost during cutover
~2h
Monday morning disruption before all staff were operational
92%
Google Drive files converted successfully on first pass