Moving to Microsoft 365 is one of the highest-value IT projects a small business can run — and one of the easiest to get wrong. Mailboxes that arrive without their folder structure, file permissions that vanish, weeks of duplicate calendars: almost every migration horror story traces back to skipped planning steps. Here is the Microsoft 365 migration checklist we use.

Phase 1 — Assess (1–2 weeks before)

• Inventory every mailbox, shared mailbox, distribution list, and alias.
• Map your file shares: what moves to SharePoint, what moves to OneDrive, what gets archived.
• Identify line-of-business apps that send email (scanners, accounting software, website forms) — these break silently if forgotten.
• Choose the right licence mix. Business Premium includes the security stack (Intune, Conditional Access) that most SMBs should be using.

Phase 2 — Prepare

• Verify your domain in Microsoft 365 and pre-stage DNS records with a low TTL so cutover is fast.
• Enable multi-factor authentication from day one — not as a phase-two cleanup.
• Communicate the plan to staff: what changes, when, and who to call.

Phase 3 — Migrate

• Run a pilot with two or three users before moving everyone.
• Migrate mail in stages, keep the old system read-only during cutover, and reconcile item counts.
• Move files with permissions intact, then spot-check sensitive folders.

Phase 4 — Harden and optimize

• Apply a security baseline: Conditional Access, anti-phishing policies, and device enrolment in Intune.
• Set up backup for Microsoft 365 — Microsoft replicates your data, but retention is not backup.
• Train staff on Teams and SharePoint so the new tools actually get used.

As a Microsoft Solutions Partner for Modern Work, OPUS Consulting Group has run this playbook for organizations across the Lower Mainland — including migrations from on-premises Exchange, Google Workspace, and aging file servers. If a migration is on your roadmap, call 1-866-800-OPUS (6787) or contact us for a fixed-scope assessment.

Common Microsoft 365 migration mistakes to avoid

• Cutting over DNS before mailboxes finish syncing, which bounces inbound email.
• Forgetting the printers, scanners, and apps that relay mail through the old server.
• Leaving security at defaults instead of enabling multi-factor authentication and Conditional Access from day one.
• Treating Microsoft 365 as a backup. It isn’t — you still need a separate backup after you migrate.

How long does a Microsoft 365 migration take?

For most small businesses a clean migration runs one to three weeks end to end, with the cutover happening over a single weekend. The variables are mailbox size and count, how much file-share data is moving to SharePoint and OneDrive, and how many line-of-business apps need reconfiguring. Thorough assessment up front is what keeps that timeline predictable.

Should you migrate yourself or use a partner?

A very small team with simple needs can self-migrate with Microsoft’s own tools. Once you have shared mailboxes, layered permissions, compliance requirements, or business-critical apps tied to email, a Microsoft partner pays for itself by preventing downtime and data loss. As a Microsoft Solutions Partner, OPUS plans and runs the cutover, hardens your security stack, and sets up the data backup most businesses overlook — see our cloud migration services for the full process.

Planning a move to Microsoft 365 in Vancouver? Contact OPUS Consulting Group or call 1-866-800-OPUS (6787) for a migration plan tailored to your business.

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