What to Clean Up Before You Move Mail, Files, and User Access
Most Microsoft 365 migrations fail long before cutover day. The real damage comes from messy identities, unclear mailbox ownership, stale shared drives, and rushed user communication. If you are moving from Google Workspace to Microsoft 365, the migration itself is only one part of the project. The rest is planning the tenant you want to land in.
1. Audit Accounts Before You Touch Mail Flow
Start with the user list. Identify active users, shared accounts, service accounts, aliases, and groups. In many Google Workspace environments, shared identities and old mailboxes linger because nobody wants to break a workflow. That becomes a problem during migration because every ambiguous account creates uncertainty about where mail and access should land in Microsoft 365.
Document who owns each mailbox, who needs delegation, which accounts can be retired, and which groups should become Microsoft 365 groups or distribution lists. If you skip this step, the migration turns into a permission hunt after users are already in the new platform.
2. Decide on Identity Before You Migrate Data
Microsoft 365 is not just email and Office apps. It is an identity platform. Decide early whether Microsoft Entra ID will be the primary identity provider, whether a third-party tool like Okta is staying in place, and how MFA and conditional access will be enforced. This decision affects onboarding, SSO, device compliance, and security policy after cutover.
3. Separate What Is Mail, What Is Files, and What Is Collaboration
Google Workspace tends to blur the lines between personal Drive, shared drives, and informal file-sharing links. Microsoft 365 requires more intentional structure. Decide what belongs in OneDrive, what belongs in SharePoint, and what should become Teams-backed collaboration spaces. If you dump everything into OneDrive because it feels easy, you will spend the next year trying to undo the sprawl.
At minimum, identify shared drives that need to become SharePoint document libraries, sensitive data sets that need tighter access, and legacy files that should be archived instead of migrated.
4. Plan the DNS and Mail Cutover Path
Mail flow changes are where leadership starts to panic, so plan them in detail. Confirm domain ownership, review existing DNS records, decide on a cutover window, and document rollback steps. Also decide how to handle devices with cached mail, mobile clients, and shared inbox workflows after the switch.
5. Train Users on the Differences, Not the Marketing
Your users do not need a generic product demo. They need to know what is changing in their actual workflow. Show them how shared mailboxes work, where files will live, how Teams differs from Google Chat or Meet, and how MFA enrollment will happen. Keep the training short, practical, and role-specific.
6. Use the Migration to Tighten Security
A platform change is the right moment to enforce better standards. Roll out MFA, clean up admin roles, remove stale access, and review external sharing before the environment settles into a new steady state. If Copilot or advanced collaboration tooling is on the roadmap, do the permissions cleanup now while the project already has executive attention.
7. Validate the First Two Weeks
The project does not end when mail starts flowing into Outlook. The first two weeks after cutover usually reveal the hidden dependencies: shared mailboxes nobody documented, calendar permissions that matter to executives, or data that landed in the wrong place. Build a short post-migration support period into the project and use it to stabilize the environment.
Key Takeaways
- Clean up users, shared accounts, groups, and mailbox ownership before the migration window opens.
- Define the Microsoft 365 identity, security, and file-governance model before moving data.
- Plan DNS, cutover validation, and user training as first-class parts of the project instead of last-minute tasks.