Read a piece today on why M365 tenant-to-tenant migrations fail. Most of the failure...

Read a piece today on why M365 tenant-to-tenant migrations fail. Most of the failure modes on the list weren't tooling problems. They were planning and validation problems that showed up as tooling problems on cutover weekend. A few patterns I've watched repeat in the field: The discovery phase gets compressed because someone assumes the source tenant is well-documented. It never is. Shared mailboxes, delegated permissions, retention policies, and third-party app registrations are almost always undercounted. Testing is treated as a checkbox instead of a wave. If your test users are all IT staff on clean laptops, you have not tested anything. You need messy real-world mailboxes, shared calendars, and someone who lives in Teams chat history from four years ago. The target tenant gets stood up in parallel with migration prep instead of ahead of it. Then licensing, domains, and identity sync issues surface during pilot instead of before it. Runbooks read well in a doc and fall apart when nobody assigned the actual human who runs step 14 at 2am. None of this is exotic. It's the boring middle of the project that determines whether the cutover feels like a non-event or a Monday morning fire. The teams I've seen do this well spend more time on target readiness and pilot design than on the migration engine itself. That ratio tells you a lot about how it will land.