Anonymized engagement summary: consolidating four acquired companies' Office 365 tenants into one parent tenant (2023)
Contracted — countersigned (EPC-reported; documents private)First-pass editionA multi-company security-systems integrator, engaged through an IT services partner (neither named) · 2023 · Project ID EPC-2023-ANON-T2T-CONSOLIDATE4
Last updated by Errin O'Connor, Founder & Chief AI Architect, EPC Group
Opening answer. In October 2023 an IT services partner engaged EPC Group to consolidate the Office 365 tenants of four companies its end client had acquired into one central parent tenant — Exchange Online mailboxes, SharePoint content, OneDrive and Microsoft Teams. The countersigned statement of work set out four phases over an estimated nine to thirteen weeks. By late October 2023 EPC Group had produced a phased project plan, a weekly status report and an assessment workbook for each of the four source tenants.
Disclosure. This is an EPC-reported anonymized engagement summary. Neither the partner nor the end client is named. The supporting records — the countersigned statement of work, the project plan, the status report and the assessment workbooks — are retained privately and are not published in the Evidence Center, so this account is outside the Evidence Center's documented-engagement counts. Every engagement fact below is taken from those documents.
Verification class
Contracted — countersigned (EPC-reported; documents private). The statement of work was executed electronically in October 2023. The project plan, status report and assessment workbooks are dated October 2023. No acceptance record, cut-over record or outcome measurement is claimed here.
Buyer problem and scope
| Item | What the documents state |
|---|---|
| Buyer | An IT services partner delivering for its end client, a multi-company security-systems integrator (neither named) |
| Situation | Four acquired companies each ran their own Office 365 tenant; the parent wanted one central tenant |
| Objective | A fully functional central tenant holding the four companies' mail and collaboration content, designed to scale |
| In scope | Envisioning, configuration extract and design; engage and prepare; migration and deployment into the parent tenant, including an Exchange Online four-tenant-to-one migration; post-deployment consulting; as-built documentation; weekly status reports and meetings |
| Out of scope (stated) | Power BI reports and dashboards, Power Automate workflows, Power Apps, Copilot and other AI elements; any re-architecture of the SharePoint site structure or content deduplication — site content moves to a like-for-like location if it moves at all |
| Estimated timeline | Envisioning, configuration extract and design 2–3 weeks; preparation of the central tenant 4–5 weeks; configuration and deployment 3–4 weeks; post-deployment 2–3 weeks (9–13 weeks in total, an estimate only) |
| Acceptance | Each service deliverable submitted for review; accepted, or rejected in writing within five business days |
Unknowns, not stated in the documents cited: the number of users, mailboxes or sites in each tenant, the migration tool chosen, the cut-over dates, and whether the consolidation was completed under this statement of work.
Approach and artifacts
Assess every source tenant before moving anything. The project plan opens with technical discovery for each tenant: the exact mailboxes and mail content to move, current DNS, MX records and SMTP relays, the authentication mechanism in use, applications that would need rebuilding in the target, and all content to be migrated. The client reviews the discovery results and narrows what moves before a detailed end-to-end migration plan is written.
One assessment workbook per tenant. Every workbook inventories Exchange, SharePoint, OneDrive, Microsoft 365 groups, distribution groups and users; three also list security groups and Teams groups, and the fourth goes further into mailbox and calendar permissions, mailbox forwarding, distribution-group membership and contacts. A licensing report was prepared for the first tenant assessed.
Prepare the target, then pilot. Phase 2 cleans up and archives in the sources where needed, confirms licences in the target, creates accounts, roles and groups, provisions SharePoint Online and OneDrive sites, and runs a pilot migration that the client team validates before Phase 3 moves mailboxes, SharePoint, OneDrive and Teams, followed by post-migration validation with administrators and an MX-record cut-over.
Risks stated up front. The October 17 status report records items the client had to decide or own: the licensing policy and timing in the destination tenant, which gated migration testing; whether each domain would move and who would move it at cut-over; and three Microsoft Teams constraints — migrated group chat appears posted by the migration account, guest accounts do not migrate and must be re-provisioned, and external sharing permissions do not carry over. It also records that tooling was being configured against source and target with no permission changes or production modifications to the existing environments.
Work products (dated, held privately):
| Work product | Date |
|---|---|
| Countersigned statement of work | October 2023 |
| High-level project plan, multi-tenant to parent-tenant migration (evaluate, prepare, migrate, cut-over) | October 2023 |
| Weekly status report and status-meeting agenda | October 17, 2023 |
| Licensing report for the first tenant assessed | October 17, 2023 |
| Tenant assessment workbooks — first tenant (versions 1 and 2) and the other three tenants | October 13–24, 2023 |
Results and limitations
| Claim | Basis | Status |
|---|---|---|
| The partner contracted EPC Group to consolidate four tenants into one | Countersigned statement of work, October 2023 | Contracted (EPC-reported; documents private) |
| One tenant's assessment was complete and shared by October 17; the other three were in progress | Status report, October 17, 2023 | On file (EPC-reported) |
| Assessment workbooks exist for all four source tenants | Workbooks dated October 13–24, 2023 | On file (EPC-reported) |
| The consolidation was completed, cut over or accepted | No document cited | Not claimed |
Provenance
- Sources: the countersigned statement of work (October 2023), the high-level project plan, the October 17, 2023 status report and the per-tenant assessment workbooks, held privately. Engagement ID: EPC-2023-ANON-T2T-CONSOLIDATE4, an alias unrelated to any client's name.
- Anonymization: industry and organization type only, under EPC Group's anonymized-case rule; the partner, the end client, the acquired companies, locations, staff names and commercial terms are not published.
- Not claimed: client endorsement, completion, cut-over or any measured result.
- Author: Errin O'Connor, Founder & Chief AI Architect, EPC Group, named in the statement of work as the engagement's lead architect.
Revision history
- 2026-10-25: anonymized engagement summary published from the engagement's statement of work, project plan, status report and assessment workbooks.
Related service
Microsoft 365 tenant consolidation for mergers and acquisitions · Microsoft 365 consulting · Talk to a senior architect
Author: Errin O'Connor, Founder & Chief AI Architect, EPC Group · Published: 2026-10-25.