How to migrate from Google Workspace to Microsoft 365 without losing data

Introduction

Migrating from Google Workspace to Microsoft 365 without losing data is not just moving mailboxes: it’s about preserving processes, security and productivity without friction. This guide gives you a clear, people-first plan: honest inventory, identity and DNS choices without unnecessary jargon, security that protects without getting in the way, well-explained coexistence, and a go-live with delta sync to keep everyone included. We also link to official Microsoft and Google documentation so every step can be audited.

1. Why migrate to Microsoft 365 now

Microsoft 365 brings together collaboration (Teams, SharePoint, OneDrive), security (Defender for Office 365), identity (Microsoft Entra ID) and governance (Microsoft Purview). It’s all synchronized so IT gets a single control plane and the business gains speed.

2. Project methodology & governance

At MSAdvance we work in waves: first a small, representative pilot; then early adopters; and finally critical areas. Every wave includes delta sync, real business tests and role-based communications to minimize surprises.

2.1 Clear governance from day one

2.2 RACI (condensed)

2.3 Sample timeline

1. Weeks 1–2: Assessment & architecture.
2. Weeks 3–4: M365 security and Google prep.
3. Week 5: Pilot (10–15%).
4. Weeks 6–8: Waves 1 & 2 + delta sync.
5. Week 9: MX cutover, final UAT and stabilization.

3. Phase 0 — Discovery & assessment

3.1 Honest inventory

• Users, aliases, groups, shared mailboxes and delegations.
• Mail volume/attachments, special rules and retention.
• Room/team calendars, bookings and permissions.
• Drive/Shared Drives: size, file count, external owners, Docs/Sheets/Slides.
• Integrations: SMTP/IMAP, Apps Script, webhooks, SSO.

3.2 Data quality

3.3 Compliance & retention

Define retention and legal holds in Records Management and eDiscovery. Document who can access what and for how long.

4. Phase 1 — Identity, DNS & coexistence

4.1 Identity without headaches

• Cloud-only (Microsoft Entra ID) or hybrid model.
• Clear UPN, verified domains and MFA from day one.

4.2 Mail, MX & authentication

Coexistence avoids hard cutovers. Preparing SPF, DKIM and DMARC reduces spam and spoofing.

• SPF: configure
• DKIM: enable
• DMARC: define policy

# MX to Exchange Online Protection
MX @ 0 → company-com.mail.protection.outlook.com

# Email authentication
TXT @ "v=spf1 include:spf.protection.outlook.com -all"
CNAME autodiscover → autodiscover.outlook.com
TXT _dmarc "v=DMARC1; p=quarantine; rua=mailto:dmarc@company.com"
    

5. Phase 2 — Microsoft 365 hardening & governance

5.1 Minimum viable hardening

• MFA and Conditional Access by role/location/risk.
• Block POP/IMAP (basic auth) except for migration use: reference.
• Enable Defender for Office 365: Safe Links, Safe Attachments and anti-phishing.

5.2 Information governance (MIP & DLP)

5.3 Pre-provisioning & licenses

Pre-create users, shared mailboxes, groups and OneDrive to save time on cutover day. Reference: Microsoft Graph PowerShell.

6. Phase 3 — Google Workspace prep (OAuth, cleanup, permissions)

6.1 Cleanup

• Disable inactive accounts and close public shares.
• Freeze critical changes the week before each wave.

6.2 Delegation & APIs

Configure domain-wide delegation for the migration service account. Official guide: Google Admin.

6.3 Drive permissions

Review owners and groups; identify Shared Drives with irregular permissions and normalize them. Reference: Sharing options.

7. Phase 4 — Mail, calendars & contacts migration

The Exchange Admin Center (EAC) lets you migrate from Google in batches with delta syncs until cutover. Official guide: migrate from Google Workspace.

7.1 Recommended flow

1. Create a migration endpoint (IMAP/OAuth depending on approach).
2. Upload a CSV with users for the wave.
3. Run a pilot batch and validate rules, delegations and calendars.
4. Schedule deltas and define the MX cutover.

Connect-ExchangeOnline
New-MigrationEndpoint -Name "Gmail-IMAP" -Imap -RemoteServer "imap.gmail.com" -Port 993 -Security SSL

$csv = [System.IO.File]::ReadAllBytes("C:\Migration\users.csv")
New-MigrationBatch -Name "Batch-Gmail-01" -SourceEndpoint "Gmail-IMAP" -CSVData $csv `
  -TargetDeliveryDomain "company.onmicrosoft.com" -AutoStart -AutoComplete:$false

Get-MigrationBatch | Get-MigrationUser | Get-MigrationUserStatistics -IncludeReport
    

7.2 CSV format

8. Phase 5 — File migration (Drive/Shared Drives → OneDrive/SharePoint)

Use Migration Manager in the SharePoint admin center to move Drive and Shared Drives with identity mapping. Guide: Microsoft Learn.

8.1 Key steps

1. Configure source/target connectors.
2. Map identities and define destinations.
3. Scan, resolve permissions/ownership and push initial load.
4. Run a pre-cutover delta and validate access.

8.2 Limits & best practices

• Long paths/names: review official limits: OneDrive/SharePoint.
• Groups: Google Groups ≠ Microsoft 365 Groups; recreate and map.
• Docs/Sheets/Slides: clear conversion policy to Office formats for native editing.

9. UAT, validations & quality control

Make sure what matters to the business works as before… or better. Test with real users by role, not just IT.

10. Change management and 30–60–90 communications

10.1 Communication milestones

• T-14 days: general announcement and expectations.
• T-7 days: “what changes today”, access and support.
• Day 0: reminder, support channel and first-day guide.
• Day 7/30: productivity tips and common questions.

10.2 Role-based training

• Sales: Outlook + Teams meetings and client sharing.
• Finance: retention, labels and critical SharePoint libraries.
• Operations: Teams channels by process and shift checklists.

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11. Licensing: Business Basic, Business Standard and Business Premium

For many organizations moving from Google Workspace, the most direct options are Microsoft 365 Business Basic, Business Standard and Business Premium. Here’s a simple, practical way to choose:

12. RAID risk matrix & mitigations

13. Playbooks by scenario

13.1 Scale-up SaaS (150–300 employees)

• Pilot 10–15% with sales, support and product profiles.
• Two waves with deltas and Friday-night cutover.
• DLP for code/PII; alerts to the IT channel.

13.2 Multi-domain M&A

• Verify domains and align UPNs.
• Temporary calendar coexistence; transition to Teams (live events if needed).
• SharePoint “bridge” for combined teams.

13.3 Industry with kiosks

• Business Premium + Intune for shared devices.
• Waves by shift; signage and micro-training.
• Teams Walkie Talkie and plant-wide announcement channel.

14. Migration methods: comparison & selection

15. Operational checklists (pre, during, post)

15.1 Before migration

• Verified domains; UPN strategy decided.
• MFA and Conditional Access enabled.
• Users/licenses and OneDrive provisioned.
• Google OAuth: domain-wide delegation.
• Migration Manager connectors (guide).
• Wave-based communication and day-1 support plan.

15.2 During

• Monitor batches and retries (EAC/PowerShell).
• Resolve name conflicts and long paths.
• Run delta synchronizations.

15.3 After

• Update MX/SPF/DKIM/DMARC.
• Validate delegations, rooms and mobiles.
• Review SharePoint/OneDrive permissions and recertify access.

16. Scripts & configurations (PowerShell/JSON)

Connect-ExchangeOnline
Get-CASMailbox -ResultSize Unlimited | Set-CASMailbox -ImapEnabled:$false -PopEnabled:$false
    

{
  "displayName": "MFA required for M365-licensed users",
  "conditions": {
    "users": { "includeUsers": ["All"] },
    "clientAppTypes": ["browser", "mobileAppsAndDesktopClients"]
  },
  "grantControls": { "operator": "OR", "builtInControls": ["mfa"] }
}
    

Connect-MgGraph -Scopes "User.ReadWrite.All","Directory.ReadWrite.All","Files.ReadWrite.All"
$sku = (Get-MgSubscribedSku | Where-Object {$_.SkuPartNumber -eq "ENTERPRISEPACK"}).SkuId
Import-Csv "C:\Provisioning\users.csv" | ForEach-Object {
  $u = New-MgUser -DisplayName $_.DisplayName -UserPrincipalName $_.UPN `
    -MailNickname $_.Alias -AccountEnabled:$true `
    -PasswordProfile @{Password=$_.Password; ForceChangePasswordNextSignIn=$true}
  Set-MgUserLicense -UserId $u.Id -AddLicenses @{SkuId=$sku} -RemoveLicenses @()
  Invoke-WebRequest -Uri "https://graph.microsoft.com/v1.0/users/$($u.Id)/drive" -Headers @{Authorization="Bearer $((Get-MgContext).AccessToken)"}
}
# Doc: https://learn.microsoft.com/en-us/powershell/microsoftgraph/overview
    

EmailAddress,UserName,Password
ana.perez@company.com,ana.perez@company.com,TempPwd#1
juan.garcia@company.com,juan.garcia@company.com,TempPwd#2
    

# Tag external subjects and block executable attachments
New-TransportRule -Name "Tag External" -SentToScope NotInOrganization -PrependSubject "[EXTERNAL]"
New-TransportRule -Name "Block executables" -AttachmentExtensionMatchesWords @("exe","js","vbs") -DeleteMessage $true

# Reference:
# https://learn.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/mail-flow-rules
    

17. Success KPIs & adoption analytics

18. Frequently asked questions (FAQ)

19. Glossary

• Delta sync: incremental synchronization prior to cutover.
• EOP: Exchange Online Protection (routing and filtering).
• MIP: Microsoft Information Protection (labels/encryption).
• Entra ID: Microsoft’s cloud identity (formerly Azure AD).
• DLP: Data Loss Prevention.

20. Official resources

• EAC: migrate from Google Workspace
• Migration best practices
• Migration Manager (Google Drive → OneDrive/SharePoint)
• OneDrive/SharePoint limits
• Conditional Access (Entra ID)
• Defender for Office 365
• Google: Domain-wide Delegation
• Google Drive: sharing options
• Microsoft Graph PowerShell
• POP/IMAP in Exchange Online

21. Conclusion & next steps

Migrating from Google Workspace to Microsoft 365 without losing data is absolutely achievable when you follow a structured path: inventory, well-planned identity/DNS, security that supports users, meaningful pilots, wave-based execution with delta sync, serious UAT and clear communications. With native tools (EAC and Migration Manager) and sound practices, go-live becomes predictable and adoption rises naturally.