Migrating from Gmail (Google Workspace) to Office 365 (Microsoft 365) is a strategic move for enterprise organizations looking to consolidate on the Microsoft ecosystem. A successful migration requires careful planning for email, contacts, calendar, and Drive data transfer, along with DNS cutover, user onboarding, and coexistence management. This guide provides the complete step-by-step process for executing a Gmail to Office 365 migration with minimal disruption.

Pre-Migration Planning and Assessment

Before initiating any data transfer, thorough planning ensures a smooth migration with minimal business disruption and data loss.

Inventory your Google Workspace environment — Document the number of users, total mailbox sizes, shared drives, calendar resources (rooms, equipment), and third-party integrations
License planning — Purchase Microsoft 365 licenses (E3, E5, or Business Premium) for all users before migration; ensure Exchange Online mailboxes are provisioned
Domain verification — Add and verify your domain in the Microsoft 365 admin center using TXT or MX records (do not change MX records yet)
User account creation — Create user accounts in Microsoft 365 either manually, via CSV import, or through Azure AD Connect if you have on-premises Active Directory
Communication plan — Notify users about the migration timeline, what to expect, and any required actions (e.g., installing Outlook, reconfiguring mobile devices)
Data cleanup — Have users archive or delete unnecessary emails and files before migration to reduce transfer time and storage requirements

Migration Methods: Choosing the Right Approach

Microsoft and third-party tools offer several migration methods. The best approach depends on your organization's size, complexity, and coexistence requirements.

Method 1: IMAP Migration (Built-in)

Uses the Exchange admin center migration wizard to connect to Gmail via IMAP
Migrates email only (not contacts, calendars, or Drive files)
Requires enabling IMAP access and creating an app password in Google Workspace admin
Best for: Small organizations (under 150 users) with simple email-only requirements
Limitation: Maximum 50 GB per mailbox; does not migrate folder structure beyond top-level

Method 2: Google Workspace Migration for Microsoft Outlook (GWMMO)

Google's free tool that exports Gmail, contacts, and calendar data to a PST file
Users import the PST into Outlook — suitable for user-driven migration
Best for: Small teams where users can manage their own migration
Limitation: Not suitable for enterprise scale; relies on individual user action

Method 3: Third-Party Migration Tools (Recommended for Enterprise)

BitTitan MigrationWiz — Automated migration of email, contacts, calendars, and Drive to OneDrive; supports batch scheduling and delta sync
Quest On Demand Migration — Enterprise-grade migration with project management, reporting, and coexistence features
AvePoint Fly — Migrates Google Workspace content to Microsoft 365 including Shared Drives to SharePoint
CloudM — Specialized Google-to-Microsoft migration with detailed mapping and scheduling capabilities
Best for: Organizations with 150+ users, complex Google Workspace environments, or strict coexistence requirements

Step-by-Step IMAP Migration Process

In Google Workspace admin, enable IMAP access for all users: Admin console > Apps > Google Workspace > Gmail > User settings
If 2-factor authentication is enabled, create app-specific passwords for each user or use a service account with domain-wide delegation
In the Exchange admin center, go to Migration > Migration batches > New migration batch
Select Migration to Exchange Online and choose IMAP migration
Upload a CSV file with user email addresses, passwords (or app passwords), and IMAP server (imap.gmail.com)
Configure the migration batch settings: target delivery domain, items to exclude, and start time
Start the batch — monitor progress in the migration dashboard
After initial sync completes, perform a delta sync before DNS cutover to capture recently received emails

DNS Cutover and Post-Migration Steps

The DNS cutover is the point of no return — after updating MX records, new email flows to Microsoft 365 instead of Google Workspace.

Schedule the cutover during a low-traffic window (e.g., Friday evening or weekend)
Perform a final delta sync in the migration batch to capture the latest emails
Update your domain's MX records to point to Microsoft 365 (e.g., yourdomain-com.mail.protection.outlook.com)
Update SPF record to include include:spf.protection.outlook.com
Configure DKIM signing in Microsoft 365 Defender for email authentication
Set up DMARC record to enforce email authentication and prevent spoofing
Update Autodiscover CNAME record for Outlook auto-configuration
Reconfigure mobile devices to connect to Exchange Online instead of Gmail
Decommission Google Workspace accounts after a coexistence period (typically 30-90 days)

Migrating Google Drive to OneDrive and SharePoint

Email is only part of the migration. Google Drive files, including My Drive and Shared Drives, need to be moved to OneDrive for Business and SharePoint Online.

SharePoint Migration Tool (SPMT) — Free Microsoft tool that supports Google Drive to OneDrive/SharePoint migration with permission mapping
Migration Manager — Cloud-based migration management in the SharePoint admin center; supports scheduling, monitoring, and reporting
Third-party tools — BitTitan, AvePoint, and CloudM support Drive migration with file conversion (Google Docs to Office format) and permission mapping
Shared Drives — Map Google Shared Drives to SharePoint document libraries or Teams channels based on the content's purpose and audience

Why Choose EPC Group for Email Migrations

EPC Group has over 28 years of experience executing large-scale email and collaboration migrations for enterprise organizations. As a Microsoft Gold Partner, we have migrated organizations with 10,000+ mailboxes from Google Workspace, Lotus Notes, GroupWise, and on-premises Exchange to Microsoft 365. Our founder, Errin O'Connor, authored the bestselling Microsoft Press book on large-scale migrations and leads a team of certified migration specialists.

End-to-end migration project management from assessment to decommissioning
Enterprise migration tool selection and deployment (MigrationWiz, Quest, SPMT)
DNS cutover planning and execution with rollback procedures
User training and adoption programs for Outlook, Teams, and OneDrive
Post-migration optimization and support

Planning a Gmail to Microsoft 365 Migration?

EPC Group's migration specialists can assess your Google Workspace environment, plan the migration, and execute the cutover with minimal downtime. Contact us for a migration assessment.

Schedule a Consultation Call (888) 381-9725

Frequently Asked Questions

How long does a Gmail to Office 365 migration take?

Migration duration depends on the volume of data and number of users. A small organization (50 users, average mailbox size) can typically complete migration in 1-2 weeks including planning and testing. Large enterprises (1,000+ users) should plan for 4-8 weeks, with pre-staging of data to minimize cutover downtime.

Will users lose any data during the migration?

With proper planning, no data should be lost. Third-party migration tools perform delta syncs that capture new emails received during the migration window. Labels in Gmail are converted to folders in Outlook, though some label structures may require manual mapping. Google Docs are converted to Office formats, and while formatting is generally preserved, complex documents should be reviewed after migration.

Can I run Google Workspace and Microsoft 365 simultaneously?

Yes. A coexistence period is recommended where both platforms run simultaneously. During coexistence, MX records point to one platform (the destination), and mail forwarding rules ensure users on both platforms continue to receive email. Most organizations maintain coexistence for 30-90 days before fully decommissioning Google Workspace.

Do Google Docs convert to Microsoft Office formats?

Yes. Google Docs convert to .docx, Google Sheets to .xlsx, and Google Slides to .pptx during migration. Most formatting is preserved, but complex features like Google Docs comments, suggestions, and collaborative editing history may not transfer fully. Google Forms and Sites require separate migration planning.

What happens to Gmail labels during migration?

Gmail labels are converted to Outlook folders during IMAP and third-party tool migrations. Since Gmail allows a single message to have multiple labels (appearing in multiple locations), while Outlook uses a single-folder structure, emails with multiple labels are typically migrated to the first matching folder. Third-party tools like MigrationWiz offer configurable label-to-folder mapping for more control.