UK consultancy — Microsoft 365 tenant migration & rescue.

The brief

The consultancy had relocated its business to the UK, but its Microsoft 365 estate hadn’t come with it: the mailboxes, OneDrive data and — critically — the company’s own domain all sat inside a tenant created and controlled by a previous provider overseas. The provider had gone quiet. The client had working email and user logins, but no administrative access, no visibility, and no way to leave. Every day the business ran on infrastructure someone unresponsive could switch off.

The requirement: get the domain, the data and the users into a new tenant owned and billed in the client’s own name — without losing the mail history, and without depending on the old provider’s cooperation.

The engineering

This was a migration with one hand tied: admin-level migration tooling needs access to both tenants, and we only had one side. So it was done manually, and documented at every step. First, the risks were put in writing — what could be preserved with user-level access only, what might not survive — and the client’s go-ahead was recorded before anything was touched. Rescues without paperwork are how disputes start.

Backups came next, at user level: full PST exports of both mailboxes — one inbox alone held close to ten thousand items — plus OneDrive contents, verified locally before the migration moved an inch. A new Microsoft 365 tenant was then built under the client’s own identity and billing, configured with multi-factor authentication and sensible defaults from the first login.

The hard part was the domain. It couldn’t be released from inside the old tenant — no admin access — so we worked Microsoft’s formal process instead: proving the client’s control of the domain at the registrar, adjusting DNS verification records, and coordinating with a Microsoft engineer to detach the domain from the old tenant. The cutover ran inside a planned downtime window the client had communicated to their contacts in advance — a controlled pause, not an outage. Domain onto the new tenant, users recreated, mail history imported, MX records repointed.

Then the cleanup that separates a migration from a tidy one: mobile devices carried cached identities pointing at the dead tenant, so sign-ins were rebuilt cleanly; lingering connections to the old organisation’s SharePoint were documented for the client’s records; and every credential — tenant, registrar, DNS — was handed over in the client’s name.

The outcome

The consultancy now owns its own front door: tenant, domain, billing and every password, held by the business instead of a stranger abroad. Years of mail history survived a migration that had no right to be easy. And the arrangement that caused the problem — a provider owning the client’s identity — is structurally impossible to repeat, because that’s the one thing we never do.

Work delivered

Client identity is withheld. A reference can be arranged privately on request.