M365 Migration
A fixed-scope migration into Microsoft 365, covering mailboxes, files, and identities, delivered on a known timeline with a known price. Whether you are coming from Google Workspace, on-prem Exchange, another M365 tenant, or a sprawl of Dropbox and Drive shares, you get a clean cut-over with zero data loss and zero working-day downtime. The same accelerator handles M&A tenant consolidation when an acquisition lands two M365 estates in the same group.
Why most migrations land badly when nobody owns them end-to-end.
Most mid-market migrations go wrong in the same three places: a discovery phase that misses the messy edge cases (shared mailboxes, calendar delegations, public folders, third-party app integrations, that one MFD that scans-to-email), a cut-over weekend that runs without a real rollback plan, and a “go-live” that hands users a new mailbox with none of their rules, signatures, or distribution lists working. The result is a week of helpdesk pain, a quiet write-off of whatever data did not come across, and a project nobody wants to talk about again.
The accelerator exists because mid-market firms do not want a six-figure systems integrator engagement, but they also cannot risk doing this with whoever is free on the IT team next month. They want a fixed scope, a fixed price, somebody who has done it many times, and a clean exit.
It is also the offer most often called in by acquirers. When a deal closes and the target arrives with their own M365 tenant — or worse, a half-finished one — the integration timeline is usually measured in weeks, not quarters, and getting the basics consolidated cleanly is what unblocks everything else.
What the migration covers.
1
Discovery & Plan
Source environment audit (mailboxes, sizes, shared resources)
File share and cloud storage inventory
Identity and group mapping
Third-party integrations (scanners, line-of-business apps, signing tools)
2
Identity & Tenant
M365 tenant prep or consolidation (incl. target-tenant standardisation for M&A)
Azure AD / Entra ID configuration
Domain verification and DNS plan
Licence allocation and assignment
3
Mailbox migration (Exchange, Google, IMAP, M365 → M365)
Shared mailboxes, distribution lists, calendar permissions
MX cut-over and mail flow validation
Signatures, rules, and delegation re-creation
4
Files & Collaboration
Dropbox / Google Drive / file-share → OneDrive and SharePoint
Permission mapping (no oversharing introduced)
Teams provisioning where in-scope
Link integrity and shortcut handling
5
Cut-over & Hypercare
Cut-over runbook with rollback positions
Out-of-hours cut-over window
30 days of post-migration hypercare
End-user comms templates and quick-reference guides
Deliverables you can hold us to.
✓
Migration plan document with scope, sequence, and rollback positions for each phase
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Full pre-migration discovery report covering mail, files, identity, and third-party dependencies
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Tenant configuration baseline aligned to Microsoft security defaults
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Data integrity report showing what was migrated, what was excluded by design, and any items quarantined for review
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Cut-over runbook your IT team can keep and reuse on the next acquisition or migration
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End-user comms pack (announcement email, day-one quick-start, support routing)
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60-minute go-live walkthrough with your IT lead
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30 days of hypercare via a dedicated Teams channel
Mid-market firms moving into Microsoft 365 from Google Workspace, on-prem Exchange, hosted Exchange, or another M365 tenant. Especially relevant if:
- You have grown by acquisition and need to consolidate inherited tenants into a single M365 estate (M&A tenant-to-tenant).
- A deal has just closed and you have 30–60 days to get the target onto your mail, files, and identity stack so the rest of the integration can start.
- You are coming off a legacy file-share or Dropbox sprawl and want to land properly in OneDrive and SharePoint without recreating the mess.
- You have tried a self-serve migration tool and hit the messy 10% that those tools never handle.
- You have a regulatory or audit reason to prove the migration was done with a documented chain-of-custody.
Tenant-to-tenant M&A migration is covered at the 250–500 user tier. If your situation is bigger — multiple tenants to consolidate, on-prem Exchange or Active Directory still in the mix, or a target that has not yet picked a destination — we scope it as a bespoke M&A IT integration engagement (Cloudbliss M&A Technology Readiness) rather than running it through the accelerator.
How it runs.
1
Kickoff
Week 1, 60 minutes. Source environment audit access, scope sign-off, cut-over date provisionally booked.
2
Discovery & Pilot
Week 1–2. Full inventory, identity mapping, third-party dependencies identified. Pilot migration of 5–10 users to validate the approach end-to-end.
3
Bulk Migration
Week 2–5 depending on volume. Mailboxes and files migrated in waves, running in parallel to your live environment so nobody loses a working day.
4
Cut-over
Out-of-hours, typically a Friday evening or Saturday. MX cut-over, final delta sync, validation against the runbook.
5
Hypercare
30 days. Dedicated Teams channel, daily check-ins in week one, weekly thereafter. We close the engagement only when your IT team signs off.
The price band, and how it lands.
Up to 25 users
£1,800
Single source, single domain, mail + OneDrive
25 – 100 users
£3,200
Mail + OneDrive + SharePoint sites, single source
100 – 250 users
£4,800
Multi-source or multi-domain, includes Teams provisioning
250 – 500 users
£6,500
Tenant-to-tenant, M&A consolidation, complex permissions
Related work
Often paired with this accelerator.
Common questions.
How long will my users be without email?
Zero working-day downtime by design. Mailboxes migrate in waves alongside your live environment, and the MX cut-over happens out of hours — typically a Friday evening or Saturday. Users finish on the old system and start the next working day on the new one, with mail flowing throughout.
What happens to mail that arrives during the cut-over?
Nothing is lost. We run a final delta sync after the MX cut-over to capture anything that arrived during the switch, then validate mail flow against the runbook before we call the cut-over complete.
Do calendar invites, shared mailboxes, and distribution lists come across?
Yes. Shared mailboxes, distribution lists, calendar permissions and delegations are part of the Mail workstream, and we re-create signatures, rules and delegation on the target so your users are not rebuilding them by hand.
Can you migrate from Dropbox or Google Drive without breaking shared links?
Yes. The Files & Collaboration workstream includes permission mapping and link-integrity handling, so shared content lands in OneDrive and SharePoint without introducing oversharing or dead links.
We have already started a migration that stalled — can you take over?
Often — about two-thirds of our migration clients come to us after a previous attempt stalled. We start with a discovery pass on the current state, identify what did and did not come across, and re-plan from there with a proper cut-over and rollback position.
What about Teams chat history and channel files?
Teams provisioning and channel files are handled where in scope. Chat-history portability depends on the source system and is confirmed during discovery — we tell you exactly what will and will not carry over before any data moves.
Do you handle tenant-to-tenant migrations for M&A, and what is the realistic timeline post-close?
Yes. The standard tenant-to-tenant pattern — mail, OneDrive, SharePoint, identity and a clean cut-over — sits at the 250–500 user tier and is typically delivered inside the 30–60 day window most post-close integrations work to. Larger or multi-tenant consolidations are scoped as a bespoke M&A engagement.
Can the source company keep using their old tenant during the cut-over window?
Yes. Migration runs in parallel with the live environment, so the source stays in use right up to the out-of-hours cut-over. The rollback position in the runbook means we can revert if anything unexpected surfaces on the night.
What is in scope vs out of scope for the fixed price?
The fixed price covers the five workstreams scoped and signed off in discovery. Anything outside that — a significant on-prem footprint, 500+ users, or multi-target M&A consolidation involving three or more tenants — is flagged before it starts and scoped separately, never invoiced after the fact.