Microsoft 365 Tenant-to-Tenant Migration: What Moves, What Does Not

Microsoft's native tooling covers mailboxes, OneDrive accounts and SharePoint sites. Everything else, Teams channels and chats above all, is rebuilt in the target tenant or moved with a third-party tool. The table is the article in one view; the sections give the limits behind each row.

Decision rule: under about 300 users, the native tools plus a Teams tool are enough. For a divestiture that must leave data behind, read splitting a tenant after a divestiture first; for the governance side of a merger, the merger operating model.

Cross-tenant User Data Migration is a per-user, one-time license that covers both the mailbox move and the OneDrive move for that user, assigned on the source user or the target user. Microsoft lists it as an add-on to the Microsoft 365 Business, Enterprise and Frontline plans, the Office 365 plans, Exchange Online, SharePoint and OneDrive. Microsoft's documentation is blunt: migrations fail without it and Microsoft offers no exceptions.

Cross-tenant Shared Data Migration covers SharePoint sites and is sold per 100 GB moved; Microsoft's documentation makes it available to Enterprise Agreement customers. Size it by summing StorageUsageCurrent across the sites in scope plus about a fifth for growth.

Both are on the October 2026 price list: Cross-tenant User Data Migration is $15.00 per user and Cross-Tenant Shared Data Migration is $48.00 per 100 GB unit; the plan pages are Cross-tenant user data migration and Cross-Tenant Shared Data Migration. Microsoft bills them to you.

The target tenant also needs ordinary licenses before any mailbox lands. At Microsoft list price, October 2026 price list, per user per month on an annual commitment: Microsoft 365 Business Basic $7.00, Business Standard $14.00, Business Premium $22.00, Microsoft 365 E3 $39.00, Exchange Online Plan 1 $4.00, Plan 2 $8.00. Both tenants are paid for during the overlap, typically 30 to 60 days.

The move runs from the target tenant as a migration batch. The target administrator registers the Move Mailbox application and creates a migration endpoint and an organization relationship pointing at the source; the source administrator consents and creates the matching relationship. Then New-MigrationBatch syncs the mailboxes.

Every mailbox needs a MailUser in the target carrying the source's ExchangeGUID, its ArchiveGUID if it has an archive, its LegacyExchangeDN as an X500 proxy address, every other X500 address, and an ExternalEmailAddress pointing at the source mailbox. Assign the Exchange license to the target MailUser only after the ExchangeGUID is stamped; license it earlier and Exchange provisions an empty mailbox instead, and the move fails.

The traps, each from Microsoft's documentation:

• Mailboxes on any kind of hold are blocked; release the hold, move, reapply it.
• Cross-tenant mailbox and calendar permissions are not supported, so every executive and assistant with delegate access goes in the same batch.
• Keep batches at 2,000 mailboxes or fewer and submit them two weeks before cutover; syncing has no user impact.
• Mailboxes near quota fail during the move; find them first and add an archive or trim them. Auto-expanding archives move with up to 12 auxiliary archives.
• The Teams chat folder in the mailbox does not migrate; it stays searchable and exportable in the source.
• Teams meetings move, but their join links are invalid in the target; they are removed and recreated.

After the move the source mailbox becomes a MailUser that forwards to the target. Shared mailboxes move, keeping store permissions only.

Both moves run from SharePoint Online PowerShell: Set-SPOCrossTenantRelationship establishes the trust, an identity map is uploaded to the target, and Start-SPOCrossTenantUserContentMove (or the site equivalent) queues the move. Content never leaves the Microsoft cloud, a user's OneDrive is read-only for a few minutes, and a redirect is left at the old URL so existing links work until the source tenant is deprovisioned.

Microsoft's limits apply to both:

• Up to 4,000 OneDrive accounts or 4,000 sites can be queued at a time.
• Each account or site is capped at 5 TB or 1 million items, counting files, versions, folders and list rows.
• The full target path cannot exceed 400 characters, and the new tenant name lengthens every URL; shorten site and user URLs first.
• The move is one-and-done: no incremental or delta pass. Users must stop editing before their window.
• Accounts or sites with a hold policy are blocked. A source tenant with service encryption under Microsoft Purview Customer Key fails the move.
• The target OneDrive or site must not already exist. Restrict OneDrive creation in the target before anyone signs in there.

SharePoint adds its own list of things that do not travel: a Teams-connected site moves its SharePoint content only; SharePoint 2010 and 2013 workflows are recreated; apps are republished; Power Apps and Power Automate flows are rebuilt; sensitivity-label protection is not carried over, and a site holding labels with user-defined permissions cannot move until those labels are removed from the files.

No generally available Microsoft tool moves a team with its channels, conversations, tabs and apps between tenants. Rebuild: create the teams in the target, move the files through the SharePoint move above, and leave channel conversations in the source as a read-only archive. Tool: a migration product that copies channel posts with authorship and timestamps, which is what our Teams tenant-to-tenant migration service does at a $3,500 tenant fee plus a fee per team. Hybrid: tool the ten teams that matter, rebuild the rest.

One-to-one and group chats are what users ask for on day one, and Microsoft's mailbox move leaves the chat folder behind. Teams private chat migration at $7 per user plus a $1,500 tenant fee copies them; our rule is the last 12 months for everyone and full history for named roles.

Viva Engage communities, Planner plans and Forms have no native cross-tenant path either. Viva Engage tenant-to-tenant migration is $3,500 per project; Planner, Forms, flows and apps are recreated by their owners.

Decision rule: anything with fewer than 50 active users in the last 90 days is rebuilt, not migrated.

Nothing moves a user object between tenants. Target users, groups and shared mailboxes are precreated by script from an export of the source, with matching UPN prefixes and the attributes the mailbox move needs; a hybrid target provisions the MailUser objects on-premises and synchronizes them up. Entra ID tenant-to-tenant basic transition is $1,300; the staged transition for weeks of coexistence is $1,300 plus $2 per user.

Windows devices that are Microsoft Entra joined to the source must leave it and join the target. By hand that is a reset per device; with device migration automation ($6 per seat plus a $4,500 tenant fee) the user signs in once with the new account and finds their profile in place. Intune policies and Conditional Access are rebuilt in the target before the first device arrives.

The domain cannot exist in two tenants. Microsoft's removal procedure requires that the domain is not the default domain, that no user, shared mailbox, resource mailbox, contact, Microsoft 365 group, distribution list or team still uses it, and that no administrator signs in with it. So every source object is switched to its onmicrosoft.com address, the domain is removed, added and verified in the target, DNS is repointed, and every target object gets its final address. Mail sent during that gap bounces unless the MX spooler service ($2,890 per project) holds it. The outage window is in domain cutover in a tenant-to-tenant migration; the no-bounce variant of the email move is cutover email migration without downtime at $3,800 plus $35 per mailbox.

Two rules keep the eight weeks honest: nothing enters week 5 without a passed pilot, because the pilot is where X500 addresses, holds and 400-character paths show up; and the cutover weekend is booked for a date, not for "when the batches finish".

Microsoft bills its two migration licenses and the target plans to you; the fixed-price services below are IT Partner's, quoted in writing before work begins.

The migration estimator builds the sum for your own counts.

Does Microsoft have a tool for tenant-to-tenant migration?

Yes, for three workloads: cross-tenant mailbox migration, cross-tenant OneDrive migration and cross-tenant SharePoint site migration. Each needs a one-time Microsoft license, and none of them moves Teams channels, chats, Planner, Forms or Power Platform content.

What license do I need for a cross-tenant mailbox migration?

One Cross-tenant User Data Migration license per migrated user, assigned on either the source or the target object. It also covers that user's OneDrive move. Without it the batch fails, and Microsoft does not grant exceptions. It is $15.00 per migrated user (Microsoft list price, October 2026 price list).

How long does a tenant-to-tenant migration take?

About eight weeks for an organization of 50 to 300 users: two weeks of discovery and licensing, one of trusts, one pilot, two of synchronization, one cutover weekend and one of clean-up. Mailbox batches are submitted two weeks before the cutover date so the weekend only completes them.

Can both tenants keep the same email domain during the migration?

No. A domain is verified in one tenant at a time, and Microsoft's documentation also requires the source and target domain names to differ while mailboxes move. The domain is removed from the source and added to the target during the cutover window, and an MX spooler holds mail during the gap.

Do Teams chats migrate?

Not with Microsoft's generally available tooling. The mailbox move leaves the Teams chat folder in the source, where it stays searchable and exportable. A dedicated chat migration tool copies one-to-one and group chats into the target.

Will links to old OneDrive files keep working?

Yes. After a cross-tenant OneDrive or SharePoint move, Microsoft leaves a redirect at the old location, so a shared link opens the file in the new tenant as long as the person still has access there. The redirects last until the source tenant is deprovisioned.

• Cross-tenant mailbox migration — Microsoft Learn, updated 2025-09-28, checked 2026-10-11
• Cross-tenant OneDrive migration — Microsoft Learn, updated 2025-08-14, checked 2026-10-11
• Cross-tenant SharePoint migration — Microsoft Learn, updated 2025-08-14, checked 2026-10-11
• Remove a domain from Microsoft 365 — Microsoft Learn, updated 2026-04-23, checked 2026-10-11