Introduction
Enterprise Migration Solution
Cloudiway has successfully migrated over 5,000 cross-tenant projects, moving millions of mailboxes and petabytes of data with 99.9% success rate.
Microsoft 365 cross-tenant migration has become increasingly common as organizations undergo mergers, acquisitions, divestitures, and rebranding initiatives. Moving data between tenants requires careful planning and the right tools to ensure business continuity.
This comprehensive guide covers everything you need to know about cross-tenant migration: from understanding the scope of what can be migrated, to step-by-step processes, best practices, and how to overcome common challenges.
What Is Cross-Tenant Migration?
Cross-tenant migration refers to the process of moving user data, configurations, and services from one Microsoft 365 tenant (source) to another tenant (target). Unlike migrations from on-premises or other cloud platforms, cross-tenant migration involves two separate Microsoft 365 environments.
Key Characteristics
- Separate Azure AD: Each tenant has its own Azure Active Directory with distinct user identities
- Different Domains: Tenants typically have different email domains and service URLs
- Independent Services: Each tenant has its own Exchange Online, SharePoint, Teams, and OneDrive configuration
- Isolated Security: Security policies, compliance settings, and admin controls are tenant-specific
Because Microsoft 365 was designed with tenant isolation in mind, there's no built-in "move tenant" function. Data must be extracted from the source tenant and recreated in the target tenant while maintaining fidelity, permissions, and user experience.
Common Migration Scenarios
Organizations typically need cross-tenant migration for the following business situations:
Mergers & Acquisitions
Combining two organizations into a single Microsoft 365 tenant for unified collaboration and management.
Divestitures & Spin-offs
Separating a business unit into its own Microsoft 365 tenant during company split or sale.
Rebranding
Moving to a new tenant as part of company rebranding with new domain and identity.
Tenant Consolidation
Merging multiple tenants (regional or departmental) into a single global tenant.
What Can Be Migrated
Cloudiway supports comprehensive cross-tenant migration of all major Microsoft 365 workloads:
Exchange Online Mailboxes
- Emails, folders, contacts
- Calendars and appointments
- Tasks and notes
- Rules and signatures
- Archive mailboxes
Microsoft Teams
- Team structure and channels
- Conversations and chat history
- Files and attachments
- Tabs and connectors
- Team membership
SharePoint Online
- Sites and subsites
- Document libraries
- Lists and list items
- Permissions and sharing
- Metadata and versions
OneDrive for Business
- Personal files and folders
- Sharing settings
- Version history
- Permissions mapping
- Sync settings
Migration Approaches
There are several approaches to cross-tenant migration, each with its own trade-offs:
Cloudiway
Comprehensive solution with zero downtime
- Full workload coverage
- Delta synchronization
- Automated mapping
- Expert support 24x5
Microsoft Native
Built-in feature for basic migrations
- Mailbox & OneDrive only
- Complex setup required
- PowerShell expertise
- No project management
PST Export/Import
Traditional file-based approach
- Extremely slow
- High data loss risk
- No incremental sync
- Significant downtime
Step-by-Step Process
A successful cross-tenant migration follows these key phases:
Discovery & Assessment
Analyze source tenant to identify all users, groups, mailboxes, Teams, SharePoint sites, and OneDrive data. Create a detailed inventory and migration plan.
Tenant Preparation
Configure target tenant with required licenses, domains, and Azure AD settings. Set up user accounts and groups in the destination environment.
Identity Mapping
Map source users to target users, configure UPN changes, and set up mail forwarding for the transition period. Prepare distribution lists and security groups.
Pilot Migration
Migrate a pilot group to validate the process, test user experience, and identify any issues before full migration. Collect feedback and adjust settings.
Data Migration
Execute the main migration in batches. Cloudiway migrates mailboxes, OneDrive, SharePoint, and Teams in parallel while users continue working.
Delta Sync & Cutover
Perform final delta synchronization to capture recent changes. Update DNS records and switch users to the target tenant. Verify all data is complete.
Post-Migration Validation
Verify migration completeness, test all workloads, validate permissions, and provide user support. Decommission source tenant when ready.
Best Practices
Follow these best practices to ensure a successful cross-tenant migration:
Start with Discovery
Conduct a thorough assessment of your source tenant. Identify inactive users, orphaned data, and content that doesn't need to migrate.
Plan Identity Strategy
Decide how user identities will be handled: same UPN, new domain, or hybrid. This affects mail flow, Teams, and SharePoint permissions.
Communicate Early
Notify users well in advance. Provide training on any changes and set clear expectations for the migration timeline.
Migrate in Phases
Don't migrate everything at once. Start with pilot users, then migrate by department or location to manage risk and support load.
Use Delta Sync
Leverage delta synchronization to minimize the cutover window. This ensures users have the latest data without extended downtime.
Validate Thoroughly
Test each workload after migration. Verify mailbox access, Teams functionality, SharePoint permissions, and OneDrive sync.
Common Challenges & Solutions
Cross-tenant migrations present unique challenges. Here's how Cloudiway addresses them:
Coexistence Period
Cloudiway provides mail forwarding, calendar free/busy sharing, and GAL sync during the transition to maintain collaboration between tenants.
Teams Private Channels
Private channels require special handling. Cloudiway migrates private channel content while preserving membership and permissions.
Large Mailboxes
Mailboxes over 50GB are migrated using optimized threading and checkpoint recovery to ensure reliable transfer without timeouts.
SharePoint Customizations
Custom workflows, apps, and web parts are documented and recreated in the target tenant with equivalent functionality.
Compliance Requirements
Audit logs, retention policies, and eDiscovery holds are preserved and mapped to the target tenant's compliance configuration.
License Optimization
Migration is an opportunity to right-size licenses. Cloudiway's discovery helps identify inactive users and optimize licensing costs.
Get a free migration assessment from our experts. We'll analyze your tenant and provide a detailed migration plan.
Frequently Asked Questions
What is Microsoft 365 cross-tenant migration?
Cross-tenant migration is the process of moving user data, mailboxes, files, and collaboration content from one Microsoft 365 tenant to another. This is commonly required during mergers, acquisitions, divestitures, or organizational restructuring where companies need to consolidate or separate their Microsoft 365 environments.
Can Microsoft native tools perform cross-tenant migration?
Microsoft offers cross-tenant migration capabilities for mailboxes and OneDrive, but it requires complex Azure AD organization relationship setup and PowerShell expertise. For comprehensive migrations including Teams, SharePoint, and Groups with a user-friendly interface, third-party tools like Cloudiway are recommended.
How long does a cross-tenant migration take?
Migration duration depends on data volume, number of users, and workloads being migrated. A typical 1,000-user migration with mailboxes, OneDrive, and Teams can take 2-4 weeks. Cloudiway's parallel processing and delta sync capabilities significantly reduce migration time while ensuring zero downtime.
Will users experience downtime during cross-tenant migration?
With Cloudiway's migration approach, users experience zero downtime. Data is migrated in the background while users continue working. Delta synchronization captures changes made during migration, and the final cutover requires only a brief DNS change that users typically don't notice.
Are Teams conversations and files preserved during migration?
Yes, Cloudiway preserves Teams channels, conversations, files, tabs, and membership during cross-tenant migration. Private chats can also be migrated depending on compliance requirements. The full Teams structure is recreated in the target tenant.
What about SharePoint permissions and metadata?
Cloudiway preserves SharePoint site structure, document libraries, permissions, metadata, and version history during migration. Custom columns, content types, and workflows can be mapped to the target tenant's configuration.
