The brief

The client had been on Google Workspace for several years. As the business grew, they outgrew the platform's fit. Their leadership wanted to move to Microsoft 365 to align with parent group standards, gain access to Microsoft's deeper enterprise security tooling, and simplify how the wider team worked across Microsoft-centric clients and partners.

The migration needed to happen without disrupting day-to-day operations, with no loss of historical email or document permissions, and with minimal user retraining required.

What was in scope

  • Migrate all user mailboxes from Google Workspace to Microsoft 365 (Exchange Online)
  • Migrate all Google Shared Drives to corresponding Microsoft 365 SharePoint sites
  • Preserve folder structures, file metadata, and version history where possible
  • Replicate all permissions and access controls exactly, not from scratch
  • Set up Entra ID identity, conditional access policies, and security baseline
  • Configure Microsoft Teams, Outlook, and OneDrive for all users
  • Coordinate cutover with minimal user disruption
  • Document the new environment and train internal admin staff

What we did

Email migration

All user mailboxes were migrated from Google Workspace to Microsoft 365 using a managed migration platform. Mail history, calendar, contacts, and folder structures were preserved. The migration ran in parallel with the existing Google Workspace setup, so users continued working in Google while mail was copied across. Mail flow was switched at cutover, and Google Workspace was kept active in read-only mode for a fortnight afterwards as a safety net.

Shared Drive to SharePoint migration

Google Shared Drives map to Microsoft 365 SharePoint sites conceptually, but the underlying structures are different. We mapped each Shared Drive to a corresponding SharePoint site, preserving the logical structure that the client's teams were used to. Files, folders, and metadata were migrated with version history preserved where the source and destination supported it. Each SharePoint site was provisioned with appropriate hub-site associations to reflect the firm's organisational structure.

Permissions migration via API

This was the technically interesting part. Replicating permissions from Google Workspace to Microsoft 365 manually would have taken weeks and introduced errors. Instead, we exported the full Google Workspace permissions model using the Google Drive API, mapped Google identities and groups to their Microsoft 365 equivalents, and applied the corresponding permissions to SharePoint sites and folders via the Microsoft Graph API. This automated approach meant the new SharePoint structure went live with exactly the same access controls the client had on day one in Google, with zero manual permission setting and no opportunities for human error.

Identity and security

Entra ID was set up as the identity foundation, with conditional access policies enforcing MFA, device compliance, and location-based access rules. SSO was configured for the firm's other tooling where possible. A proper admin role hierarchy was established, with break-glass accounts provisioned and stored appropriately.

Cutover and support

Cutover was scheduled for a Friday evening to minimise business disruption. Mail flow switched cleanly, users picked up Outlook on Monday with full mail history intact, SharePoint sites were accessible with familiar permissions. We were on-site Monday morning and remote available all week for any issues. By the end of week one post-cutover, the firm was operating fully on Microsoft 365 with no significant disruption to client work.

The result

The firm migrated cleanly from Google Workspace to Microsoft 365 in 6 weeks end to end, with all email history preserved, all shared drives migrated to SharePoint, and all permissions replicated exactly. There was no significant business disruption, no data loss, and minimal user retraining required because folder structures and access patterns stayed familiar.

  • Zero data loss across email, Drive, calendars, contacts
  • Permissions migrated automatically via Graph API rather than manually
  • Cutover completed in a single weekend with no significant Monday morning disruption
  • Conditional access and security baseline established from day one
  • Two weeks of parallel running (Google Workspace in read-only) as a safety net
  • Internal admin team trained and equipped to manage the new environment

"The migration went better than we'd hoped. The Drive to SharePoint move was the bit we were most nervous about, and it just worked. Permissions came across exactly as they were. We barely heard from anyone on the team the Monday after cutover."

Operations Director, London-based advisory firm

Need something similar?

If you're considering moving from Google Workspace to Microsoft 365, or any platform migration, we've done it cleanly across a range of business sizes and industries. The permissions migration approach in particular is something we've refined across multiple projects.

See our Microsoft 365 services for the destination platform, our Google Workspace services for the source platform, our fractional CTO offer if you want strategic IT leadership alongside platform work, or our London IT support page for ongoing service.