Short answer
Use Microsoft's native Cross-tenant mailbox migration and cross-tenant OneDrive migration when your scope is mainly mailboxes and OneDrive and both tenants meet the prerequisites. Use a third-party migration tool when you also need Teams chats and channels, SharePoint sites, Planner or granular scheduling and reporting. Many projects combine both: native for mailboxes, a tool for collaboration content.
Key facts
- Native Cross-tenant mailbox migration moves full mailboxes, including archives, as true moves that keep item identity.
- Native cross-tenant moves require a paid per-user Cross-Tenant User Data Migration add-on license.
- Native tooling does not cover Teams chat history or general SharePoint site content end to end.
- Third-party tools are copy-based and cover more workloads, but they rebuild items rather than move them.
- Tool choice is a scope decision: list workloads first, then pick tools.
What Microsoft's native tools cover
Cross-tenant mailbox migration uses the Exchange Online Mailbox Replication Service to move mailboxes between tenants. It requires an organization relationship, a migration endpoint, an Entra ID application with consent in both tenants, and target mail users stamped with matching attributes such as ExchangeGUID and LegacyExchangeDN as an X500 proxy address. Because it is a true move, items keep their identity and the source mailbox is converted to a mail user afterward.
Cross-tenant OneDrive migration moves a user's OneDrive to the target tenant and leaves a redirect behind for a period. It is run with SharePoint Online PowerShell and needs a trust relationship set up between the two tenants first.
Both native options need the Cross-Tenant User Data Migration add-on for each migrated user. Microsoft lists this through its licensing channels; check current pricing with your licensing provider rather than relying on old figures.
- Covered natively: Exchange Online mailboxes and archives, OneDrive for Business accounts.
- Limited or not covered natively: Teams chats, Teams channel conversations, general SharePoint team sites, Planner, Forms, Power Automate flows, Power Apps, Stream content.
What third-party migration tools add
Commercial migration platforms connect to both tenants with admin-consented applications and copy content through Microsoft Graph and other APIs. They typically cover mailboxes, OneDrive, SharePoint sites, Teams teams and channels, and in many cases Teams one-to-one and group chat history.
They also add project features that native tools lack: scheduling by wave, pre-stage and delta passes, per-user reporting, permission mapping files and retry handling. For a project with hundreds of sites and teams, that reporting is often the deciding factor.
The trade-off is that tools copy rather than move. Copied items get new IDs, some metadata is rewritten, and API throttling in Microsoft 365 limits how fast large volumes can be copied.
Side-by-side comparison
The table below is a general comparison. Specific tools vary, so confirm coverage for your workloads in a pilot.
| Factor | Native Microsoft cross-tenant | Third-party tool |
|---|---|---|
| Mailboxes | Full move, high fidelity | Copy, good fidelity |
| OneDrive | Native move with redirect | Copy, with permission mapping |
| SharePoint sites | Limited | Broad coverage |
| Teams channels and chats | Not covered end to end | Usually covered, with limits |
| Licensing | Per-user add-on from Microsoft | Per-user or per-GB tool license |
| Setup effort | Higher: trust, apps, attribute stamping | Moderate: app consent and mapping |
| Reporting and wave scheduling | Basic, mostly PowerShell | Built-in dashboards |
How to decide
Start from scope. If the target is mostly email and OneDrive, the source tenant is fairly clean and you have staff comfortable with Exchange Online PowerShell, native tools can carry the project.
If Teams and SharePoint matter, or the business expects chat history to come across, a third-party tool is usually needed for at least those workloads. A hybrid approach is common: native Cross-tenant mailbox migration for high-fidelity mail, and a tool for SharePoint, Teams and anything else.
- Choose native for mail when mailbox fidelity, large archives and avoiding full Outlook resyncs matter.
- Choose a tool when you need Teams chats, SharePoint sites or wave reporting.
- Run a pilot with real data from your heaviest users and largest sites before committing to either.
- Budget for the licenses in both approaches; neither is free at scale.
Common mistakes
Teams often pick a tool before inventorying workloads, then discover mid-project that private channels, Loop components or Planner boards are out of scope. Others assume native tools handle everything and learn late that Teams content needs a separate approach.
Another mistake is ignoring throttling. Whatever the tool, Microsoft 365 limits API throughput per tenant, so large SharePoint estates need early pre-staging rather than a last-minute bulk copy.
How Accred Consulting approaches it
Accred Consulting picks tools after discovery, not before. We inventory every workload, then recommend native Cross-tenant mailbox and OneDrive migration, a third-party platform, or a mix, based on fidelity needs, volumes and licensing. The proposal names the tools, the licenses you need and a fixed price and timeline. Our US-based specialists configure tenant trusts, run a pilot on real data and manage every wave, with structured check-ins throughout. Handover includes documentation of what moved, how, and any items that need follow-up.
Track record: 400+ client projects, 2,000+ migration workstreams and 150,000+ users migrated by a US-based team. Company facts · Case studies
Related questions
Want this scoped for your environment?
Book a free consultation. After discovery you get a written plan with scope, a fixed price and a timeline.
Book a free consultation