Google Workspace to Microsoft 365: A Migration Playbook

Google Workspace to Microsoft 365 is one of the most common migration projects in enterprise IT today, and one of the most frequently underscoped. The data volumes are large, the permission models between Drive and SharePoint are fundamentally different, and Gmail's label system does not map cleanly to Outlook folders. Here is a field-level playbook based on doing these migrations at scale across healthcare, finance, and enterprise environments.

How Do You Plan a Google Workspace to Microsoft 365 Migration?

Before migrating a single mailbox, the destination M365 tenant needs to be fully configured. Domain verification in M365 must be completed using a TXT record — since you cannot transfer your MX record to Microsoft until cutover, you verify domain ownership using the MS=msXXXXXXXX TXT method without touching MX. Provision all licenses before migration begins. Running a migration against unlicensed accounts causes inconsistent failures that are difficult to diagnose.

Establish your naming convention for user accounts. In Google Workspace, UPNs are typically user@company.com. In M365, they should match — this minimizes user confusion and enables clean coexistence during the transition period. If your organization has on-premises Active Directory, users may already exist as AD accounts; the M365 identities need to be linked to those AD accounts via Entra Connect before migration so the mailbox attaches to the correct identity.

Audit your Google Workspace tenant before migration: total mailbox count and size, Drive storage per user and shared drive, active users vs. alumni accounts, distribution lists, shared calendars, and external sharing configuration. This audit drives your license selection and migration wave plan. Migrating 500 active users is a different project than migrating 350 active users plus 150 alumni-turned-distribution-lists with 10 years of archival email.

How Do You Handle Identity When Migrating from Google Workspace to M365?

If your organization has on-premises Active Directory, provision M365 accounts from AD via Entra Connect before migration. This ensures each M365 mailbox is associated with the correct on-premises identity, enabling Seamless SSO, Entra-joined device management, and a clean post-migration experience. The Entra Connect setup should complete and sync should be stable before any mail migration begins.

For cloud-only organizations (no on-premises AD), M365 accounts are created directly in Entra ID. Use a CSV import via the M365 admin center or Graph API bulk creation for large user populations. Set temporary passwords and enforce change-at-first-login. Configure MFA enrollment before or immediately after cutover — a Google-to-M365 migration is an ideal forcing function for MFA adoption since users are already reconfiguring their mobile devices.

Google Workspace uses a single unified directory. Service accounts, room resources, and shared mailboxes in Workspace need to be re-created as the appropriate M365 object types — room mailboxes, equipment mailboxes, shared mailboxes, or service accounts with Exchange Online Plan 1 licenses. Map these during planning and provision them before user migration waves begin.

How Do You Migrate Email from Google Workspace to Exchange Online?

Three primary tools handle Gmail-to-Exchange Online migration:

Native IMAP Migration (Microsoft Migration Manager): Built into the M365 admin center. Free, requires no third-party tools. Limitations: migrates only inbox and subfolders (no calendar, contacts, or tasks), no delta sync beyond the initial migration, no per-item migration reporting. Appropriate for small organizations with simple requirements and limited archival email.

BitTitan MigrationWiz: The most widely deployed commercial migration tool. Supports full mailbox migration including calendar and contacts, runs continuous delta syncs during the coexistence window, provides per-item pass/fail reporting, and handles Gmail labels as Outlook subfolder equivalents. Requires purchasing per-user migration licenses. MigrationWiz connects to Gmail via OAuth and requires granting the MigrationWiz service account domain-wide delegation in Google Workspace Admin Console.

Movebot: Strong for Drive-to-SharePoint/OneDrive; also handles Gmail migration. Simpler interface than MigrationWiz, competitive pricing. Good choice when Drive migration is the primary concern and mail is secondary in complexity.

Regardless of tool, run a pilot migration of 10–20 accounts representing different user profiles (heavy archival email, calendar-intensive, large attachments) before running production waves. Validate completeness and performance before committing to a wave schedule. Plan migration waves of 50–100 users, with 24–48 hours of delta sync running before each group's cutover date.

Gmail's 25MB attachment limit and Exchange Online's 150MB limit (for SMTP) mean most attachments migrate cleanly, but messages that were stored in Gmail as external links (Google Drive file references embedded in email) are not email attachments — they are hyperlinks and will remain as links post-migration pointing to Google Drive. These will break if the Workspace subscription is cancelled before Drive content is migrated.

How Do You Migrate Calendars, Contacts, and Google Vault to Microsoft 365?

Google Calendar and Contacts migration is included in MigrationWiz mailbox migrations. Recurring meeting series and all-day events generally migrate correctly. External calendar sharing relationships — where users subscribed to external Google Calendars — do not migrate and must be re-created. Room and resource calendar bookings migrate as data in the originating user's calendar, but the room mailboxes themselves need to be provisioned in M365 and configured separately.

If your organization uses Google Vault for email archiving and litigation hold, export Vault data before cancelling Workspace. Vault exports produce MBOX files that can be converted to PST and imported into Exchange Online via the Import tool in the Purview compliance portal. This is a one-time bulk import — build this into the project timeline. Court-ordered litigation holds in Google Vault need to be reviewed with legal counsel to determine whether the Exchange Online In-Place Hold or Litigation Hold provides equivalent preservation.

How Do You Migrate Google Drive to SharePoint and OneDrive?

Drive to SharePoint/OneDrive is typically the most complex and time-consuming component of a Google to M365 migration. The permission models are fundamentally different: Google Drive uses individual file-level sharing that accumulates over years; SharePoint uses site-level, library-level, and item-level inheritance with a breaking permissions model that gets unwieldy at scale.

My Drive (personal storage) maps to OneDrive for Business. Shared Drives (formerly Team Drives) map to SharePoint document libraries or team sites. This is a conceptual mapping, not an automatic technical one — the migration tool moves the files, but the destination site structure needs to be designed and provisioned before migration begins.

Google Drive permissions are migrated as SharePoint permissions by Movebot and similar tools, but the complexity of Drive permissions (especially items shared with "Anyone with the link") requires a governance decision before migration: do you replicate those broadly-shared links in SharePoint, or do you use migration as an opportunity to tighten sharing defaults? We recommend the latter — SharePoint's default is more restrictive than Drive's, and using migration as a reset point is cleaner than inheriting years of Drive link sprawl.

Google Docs, Sheets, and Slides are Google proprietary formats. Migration tools convert them to .docx, .xlsx, and .pptx respectively during migration. Conversion fidelity is good for standard documents but complex formatting, Google-specific features, and App Script automations do not survive conversion. Identify business-critical Workspace documents before migration and test-convert them during the pilot phase.

How Do You Handle DNS Cutover When Migrating from Google Workspace to M365?

During the migration period, keep Google Workspace as the authoritative mail system (MX pointing to Google) and run delta syncs of migrated mailboxes. Switch MX to Exchange Online only when the last user wave is complete and fully synced. The DNS cutover sequence is: lower TTL on MX record 48 hours in advance, then on cutover day update MX to Exchange Online, then update SPF to remove Google's include:_spf.google.com and add include:spf.protection.outlook.com, then enable DKIM on the M365 side, then update DMARC if present.

After MX cutover, any mail still in flight to Google will be forwarded automatically for a short window if you leave the Google Workspace accounts active. Leave them active for 48–72 hours post-cutover to catch any messages in transit, then begin the Workspace decommission process.

What Are the Most Common Google Workspace to M365 Migration Mistakes?

Gmail labels vs. Outlook folders: Gmail uses labels for organization; Outlook uses folders. Migration tools convert labels to subfolders under the inbox. Users with complex label hierarchies will find their Outlook structure unfamiliar. Set user expectations before cutover and offer a brief Outlook orientation session.

Mobile device re-enrollment: Every user needs to remove their Google Workspace account from their mobile mail client and add their Exchange Online account. In healthcare and other regulated environments, this is also the time to enforce Intune enrollment for mobile access. Do not underestimate the help desk volume spike on cutover day — plan staffing accordingly.

Google Groups vs. M365 distribution lists: Google Groups used for email distribution need to be recreated as M365 distribution lists, Microsoft 365 Groups, or mail-enabled security groups. Groups with external members (suppliers, partners) need external senders added to the allowed list in Exchange Online.

Premature Workspace cancellation: Do not cancel Google Workspace until Drive migration is fully validated, Vault exports are complete, and any Google-specific app integrations are decommissioned or reconfigured. Cancellation immediately revokes access and cannot be undone on short notice.