Our new CEO wants the organization to move from Google Workspace to Microsoft 365 by the end of the year. Most employees rely heavily on Gmail, Drive, Docs, Sheets, and Forms, although a smaller group already uses Word and Excel. We also have public-facing Google Forms, SSO integrations, Google sign-in used for Windows accounts, copier scan-to-email configurations, and likely dozens of third-party services connected through "Sign in with Google."
I was told this could be completed in roughly a month, possibly while keeping some Google services running temporarily. I'm skeptical, especially because there are more than 70 employees and only one person available internally to manage the project.
I'm considering hiring a migration specialist and arranging user training. For anyone who has completed a business-wide Google Workspace-to-Microsoft 365 migration, how difficult was it? What hidden dependencies caused problems, and what should be inventoried or tested before beginning? I'd also appreciate advice on migration tools, storage planning, document conversion, identity management, and realistic timelines.
5 Answers
The biggest surprises are usually identity and third-party integrations, not the mailbox migration itself. Inventory every application using Google SSO or OAuth, along with shared drives, service accounts, forms, scanners, meeting-room devices, Chrome profiles, and any automated workflows. Check each vendor to confirm that Microsoft identity integration is supported and determine whether existing account data will actually be preserved when users switch sign-in methods.
Use a migration partner unless you have substantial Microsoft 365 experience and enough staff to run the project without neglecting normal support. A partner can handle discovery, API setup, pilot migrations, domain and identity changes, data validation, and user training. Products such as BitTitan MigrationWiz are commonly used for mailbox and file migrations, but run a test migration first and validate permissions, converted documents, and application integrations before moving everyone.
The tool can make the transfer easier, but it cannot rebuild incompatible Google Forms, Sheets, Sites, or custom workflows automatically. Those need separate replacement projects and should be tracked independently from the email cutover.
Do a full capacity and licensing assessment before promising anything. Compare mailbox sizes with Microsoft’s limits, calculate the total content in My Drive and shared drives, and plan SharePoint and OneDrive storage early. Also account for archives, shared mailboxes, permissions, retention requirements, and file paths that may exceed Microsoft limits. Storage beyond the included allowance can become expensive if it is discovered late.
Conditional Access and identity protection licensing should be part of the design as well. Microsoft 365 E3 may cover many organizations, while some advanced identity features require Entra ID P2 or an equivalent license. Confirm the exact requirements rather than assuming the most expensive tier is necessary.
Set expectations with leadership now. You can potentially move mail and basic files quickly with enough budget and outside help, but a complete transition involves rebuilding forms, workflows, integrations, documentation, training, and support processes. A phased approach is safer: inventory everything, pilot with a small group, migrate low-risk users, keep a carefully planned coexistence period, and only retire Google services after each dependency has an owner and replacement.
Don’t treat this as a one-month project unless the environment is unusually small and simple. A realistic plan is several months for discovery, cleanup, pilot testing, migration, and user training. Gmail can often be moved relatively smoothly, but Google Docs and Sheets may need conversion and manual repair. Formatting, formulas, linked files, permissions, nested folders, Forms, Google Meet content, and Google Sites are all areas where automated migration can be incomplete or unreliable.
We spent longer on analysis and testing than on the actual cutover. Even with careful planning, users tend to have undocumented workflows and files that only become visible during the pilot.
For Google-side discovery, tools such as GAM can help identify OAuth grants and connected applications. Also have users review the applications linked to their individual accounts, since administrators may not see every personal connection.