Global Corp: 5,000-User M&A Consolidation — Global Corp

The Challenge

After acquiring a 5,000-person competitor, Global Corp needed to consolidate two separate Microsoft 365 tenants into one. The acquired company had its own domain, its own SharePoint sites, its own Teams channels, and five years of email history.

Traditional migration tools couldn't handle same-platform M365-to-M365 migration without creating duplicates or losing metadata. Previous attempts with manual PowerShell scripts had resulted in broken sharing permissions and missing calendar events.

Requirements:

Zero data loss across all 13 data types
No duplicate items (executives had been using both tenants)
Maintain original email timestamps and folder structures
Preserve all file sharing permissions
Complete within a 3-week window before the acquired domain was decommissioned

The Solution

Global Corp chose MigrateData for its same-platform tenant-to-tenant migration support, two-tier duplicate prevention, and phased rollout capabilities.

Phase 1: Discovery (Day 1-2)

MigrateData's discovery scan analyzed both tenants and identified:

5,000 user mailboxes averaging 8 GB each
2.3 TB of OneDrive files
450 shared mailboxes
200+ Teams channels
85 shared calendars

The AI pre-migration analysis flagged 12 potential issues, including shared mailboxes with conflicting names and Teams channels with external guests.

Phase 2: Wave Migration (Day 3-14)

The migration was executed in 5 waves:

Wave 1: IT team (50 users) — 4 hours
Wave 2: Executive leadership (200 users) — 6 hours
Wave 3: Sales and marketing (1,500 users) — 2 days
Wave 4: Engineering (2,000 users) — 3 days
Wave 5: Operations and support (1,250 users) — 2 days

Between waves, delta sync kept previously migrated users in sync with the source tenant.

Phase 3: Verification (Day 15)

Full reconciliation confirmed 100% data integrity across all waves. Size and name comparison verified every item.

The Results

5,000 users migrated with zero data loss
Zero duplicates — two-tier dedup caught 3,400 items that existed in both tenants
2-week timeline — completed 1 week ahead of schedule
Zero downtime — users continued working throughout migration
100% permission fidelity — all sharing permissions preserved