Google Workspace to Microsoft 365 Migration: Two Weeks of Pilot Migration Stories
Two weeks into a Google Workspace to Microsoft 365 pilot migration for a mid-size org. Thirteen mailboxes in the pilot batch. What should have been a straightforward cutover turned into a deep education in Exchange migration edge cases, MRS throttling behavior, and the gap between what Microsoft documents and what actually happens in production. The Setup The architecture: phased cutover with Mimecast coexistence routing, GAM-managed forwarding during the transition window, and batch migration via Exchange Online migration endpoints backed by a GCP service account. A verified alias subdomain (o365.[domain]) serves as the target delivery domain, with workspace.[domain] as the coexistence routing domain pointing back to Google. ...