When a tenant migration is needed
Microsoft offers no switch to move one tenant into another. Every consolidation is therefore a migration project. The most common triggers:
- Merger or acquisition: the acquired business is to join the buyer's tenant so that Teams, the address book and policies are uniform.
- Carve-out: a business unit is sold or made independent and needs its own tenant with its data.
- Consolidation: tenants of several sites or subsidiaries that grew over time become one.
- Renaming or region change: the tenant name or data region cannot be changed; a new tenant is then the cleanest way.
In every case the same framework applies as for our other services: free initial analysis, fixed price, pre-migration during normal operation, delta sync and final report. The six phases are described on the process page; the typical challenges in the guide Microsoft 365 tenant-to-tenant migration.
What is transferred between two Microsoft 365 tenants
The Microsoft 365 to Microsoft 365 route is the most complete our software handles, because source and target use the same concepts. At the fixed price we migrate mailboxes with folder structure, calendars with recurring series and attendees, personal contacts and contact groups, and OneDrive drives up to 50 GB per user. Added to that are groups and distribution lists with members and owners and, specific to this route, file and folder shares including sharing links, group ownership, and calendar sharing and delegation.
SharePoint sites, Teams files and shared mailboxes are quoted after the discovery analysis, because their scope varies greatly from tenant to tenant. Not migrated automatically: mailbox access rights, "send as" and inbox rules, site- and library-level permissions in SharePoint, the read state and categories (mail arrives as unread), exceptions of individual recurring events and secondary calendars, admin roles, security and compliance policies, and the DNS switch itself. Each of these items appears in the discovery report so that it has an owner before the cut-over date.
Google Workspace: moving to another domain
We also migrate between two Google Workspace organisations: emails with labels, calendars including single-occurrence exceptions and shared calendars, contacts, Google Drive with shares, and Google Groups. Shared drives are taken by effort. The sequence is the same as with Microsoft: create target accounts, pre-migration, remove the domain from the old organisation and activate it in the new one, switch MX, delta sync. If you are changing platform at the same time, for instance from a Microsoft tenant into the buyer's Google tenant, see Google Workspace migration and Microsoft 365 migration.
The domain switch: the one step that must be tightly timed
A domain can be verified in only one Microsoft 365 tenant or Google organisation at a time. Before it is released from the old tenant, every address, alias and group using that domain has to be moved to another domain there; only then can the domain be removed and added in the target. The users in the target then receive their final addresses and the MX records are switched. This chain cannot be spread over days; it is worked through in a fixed order within an agreed window, usually at the weekend.
Everything else is decoupled: the pre-migration fills the target tenant days or weeks beforehand while both tenants remain productive. For the transition we set up mail routing with you so that messages between the old and new environment are still delivered. After the cut-over date the delta sync picks up everything that was added since the pre-migration. Basics of the MX switch are in the guide email move without downtime (German).
Identities, mapping and name conflicts
Before the migration we map every source account to a target account. The discovery analysis surfaces the conflicts that would cause trouble later: duplicate display names, aliases that exist in both tenants, groups with the same name, users without a licence in the target. We go through this list with you before the quote. In hybrid environments with Active Directory and Entra ID Connect it must also be decided which side will own the identities in future; we plan that with your IT team and advise you on the Entra ID Connect changeover.
Data protection with several legal entities
A tenant migration often involves two companies, and both remain responsible for their data until the handover is complete. For us that changes nothing technically, but it matters contractually: we sign the data processing agreement under Art. 28 GDPR with the company that commissions the migration; whether the second legal entity also has to be included is something to clarify with your data protection officer (not legal advice). The data itself runs exclusively via our servers in Germany and the EU, with no third-party service. Both tenants are only read from or written to, never altered; the source tenant remains fully intact until you decide otherwise. General notes in the guide GDPR-compliant cloud migration (German).
Result and cost
You receive the discovery report of both tenants with mapping and conflict list, a fixed-price quote, a test migration on two or three real mailboxes, and after the cut-over the final report with validation per mailbox, folder and drive. The list prices apply: €200 project fee, €29 per mailbox for emails, €5 each for calendars and contacts, €19 per user for OneDrive. For 50 mailboxes with all four components that comes to €2,810 net, because from 50 mailboxes a 10 % discount applies to the per-mailbox total; from 100 it is 15 %, from 250 we quote individually. Run your numbers through the price calculator; the cost factors are explained in the guide What does an email migration cost?.
