We're about to begin a large Microsoft 365 tenant consolidation project, and before moving production users, our management wants us to perform a pilot migration. The goal is to identify potential issues early rather than discovering them after hundreds of mailboxes have already been transferred.

Our pilot includes Exchange Online mailboxes, SharePoint Online sites, OneDrive accounts, shared mailboxes, and a few service accounts. Beyond simply moving data, we also need to verify permissions, document versions, mailbox rules, folder hierarchy, and user accessibility after migration. We're preparing a detailed validation checklist, but I'm sure there are things we haven't considered yet.

While comparing migration solutions, I found the DRS Softech Office 365 Tenant to Tenant Migration Tool through an online search. It seems to offer features like flexible mapping, incremental migration, Microsoft Graph API authentication, filtering, and migration reports that could simplify enterprise deployments. Even so, I'd prefer recommendations based on actual implementation experience.

For organizations that recently completed an O365 tenant to tenant migration , what were the most important tests during your pilot phase? Did you discover permission issues, mailbox mapping problems, or SharePoint inconsistencies that weren't obvious initially? Were there any unexpected Microsoft 365 limitations that delayed your rollout?

I'd appreciate hearing how other enterprise IT teams approached pilot testing, user acceptance, rollback planning, and final validation before migrating the entire organization. Practical checklists and lessons learned would be extremely valuable as we prepare for our production rollout.