Migration done right is invisible

Done well, a Microsoft 365 migration should feel like a non-event to your staff. They close Outlook on Friday evening and open it on Monday morning to find everything where it was — only faster, more secure and properly backed up. Done badly, it’s a fortnight of bouncing emails, broken shared folders and angry directors.

Here’s the seven-step process Letsma uses for every M365 migration, distilled from over 100 cutovers across Surrey, Sussex and South London businesses.

Step 1 — Discovery (week 1)

We document everything before we touch anything:

• Mailbox inventory — every account, alias, distribution list and shared mailbox. Sizes and item counts matter.
• Domain audit — DNS records, current SPF, who manages the registrar.
• File storage map — shared drives, OneDrive footprints, file-share servers.
• Identity model — Active Directory, Google Workspace, or a mix.
• Application dependencies — line-of-business apps that send mail or read calendars.

Output: a discovery workbook that becomes our migration runbook.

Step 2 — Design the target tenant (week 1–2)

We pre-build the Microsoft 365 tenant before any data moves:

• Custom domain verified and DKIM/DMARC records prepared (but not switched yet).
• Entra ID baseline — MFA policies, named locations, Conditional Access in report-only mode.
• Licence plan locked in — typically Business Standard for desk workers, Business Premium for anyone with a laptop.
• SharePoint information architecture — sites, libraries, permissions structure.
• Teams and channel layout matched to your current ways of working.

Step 3 — Pre-stage the data (week 2–3)

This is the magic step that delivers zero downtime. We use a one-way sync to copy mailbox and file data into the new tenant while your old system stays live. Users keep working as normal. We typically sync every few hours, so the eventual cutover only needs to catch the last few minutes of changes.

Tools we use:

• Migration Wizard / BitTitan MigrationWiz for mailboxes
• ShareGate or Mover for file shares and Google Drive
• Native MX cutover for the final email switch

Step 4 — Train the team (week 3)

A 60-minute live session covers the differences your team will notice — usually less than people fear. We provide a branded one-page quick-start PDF for everyone, and a longer admin handbook for power users and IT contacts.

Step 5 — Cutover (Friday evening)

The actual switch typically takes 90 minutes after hours on a Friday:

1. Lower TTL on DNS records (done 24 hours in advance).
2. Final delta sync of mailboxes and files.
3. Update MX records to point at Microsoft 365.
4. Reconfigure Outlook profiles on each device (Autodiscover does most of this automatically).
5. Verify mail flow with test sends in both directions.
6. Sign off the runbook.

Step 6 — Hyper-care (Monday–Friday after cutover)

The first business day is our most-staffed day. A named engineer is on hand from 07:30 with the helpdesk pre-armed with the runbook. Typical first-day questions: “Where’s my signature gone?”, “How do I share a calendar?” and “What happened to my distribution list?” All answered in seconds because we expect them.

Step 7 — Security hardening (week +1 to +2)

With everyone migrated, we move Conditional Access out of report-only mode, enforce MFA, deploy Intune device compliance policies, switch on safe links and safe attachments, and enable OneDrive Known Folder Move so Desktop, Documents and Pictures are auto-backed up to the cloud.

What it costs

For a typical 10–30 user business migrating from Google Workspace or on-prem Exchange:

• Phase 1 — M365 setup & email migration: from £750 + VAT
• Phase 2 — Desktop/OS upgrades & Intune: from £400 + VAT
• Phase 3 — Mobile device management: from £500 + VAT

Plus your Microsoft 365 licence cost. Annual billing reduces this further.

How long does it really take?

From kick-off to fully cut over: typically 3–4 weeks for 10–30 users. Most of that time is project management and training — the technical migration itself is mostly automated background sync.

“We moved 28 staff from Google Workspace to Microsoft 365 over a Friday night and the only thing anyone noticed was a slightly different Outlook icon. Exactly what we needed.”

— Operations Manager, Croydon

Ready to start?

Book a free migration scoping call — we’ll spend 30 minutes understanding your current setup and give you a realistic timeline and quote.

Related reading: Microsoft 365 at Letsma · Cyber Security · Unlimited helpdesk