CMSIT BUSINESS GUIDE

Microsoft 365 migration checklist for your business

By CMSIT · Published 26 October 2026

Moving business email and files needs a clear scope, ownership and an agreed handover. Before comparing migration quotes, identify what must move, what must keep working and who will support your team afterwards. This checklist helps you prepare a discussion with a migration provider.

1. Define the move before choosing a plan

Are you moving email from another provider, files into SharePoint or OneDrive, or users between Microsoft 365 tenants? These are different projects. List the source and destination, approximate users, shared mailboxes, file volumes, sites and business applications. Flag archives, calendars, permissions and integrations that need separate assessment.

2. Confirm who controls the environment

• Identify the business owner of the domain, DNS, current subscriptions and destination tenant.
• Agree how the outgoing provider will transfer documentation and authorised access.
• List printers, scanners, websites and applications that send email.
• Record renewal dates and any restrictions on leaving the current arrangement.

Do not put passwords, recovery codes or customer records in an enquiry. Agree a secure access process after the scope and authority are established.

3. Ask for a pilot and acceptance checks

A representative pilot can expose mailbox, sign-in and application issues before a wider move. Ask what will be checked and who signs it off. Microsoft's custom-domain pilot guidance explains why domain and mail-routing arrangements need planning. The right migration method depends on the starting environment.

4. Agree the cutover and recovery plan

Have the provider document the change window, expected impact, communication, DNS responsibilities and escalation contact. Define how incomplete transfers or failed checks will be handled, and when the old service can safely be retired. Do not cancel it merely because copying has started.

• Check external and internal mail flow, aliases and shared mailbox access.
• Check Outlook, mobile sign-in and relevant sending devices.
• Check file access, sharing permissions and important workflows.
• Agree post-migration support, outstanding items and owner sign-off.

5. Compare project costs separately from subscriptions

Ask which discovery, preparation, migration tools, user assistance, after-hours work and follow-up are included. Clarify recurring licences, support, backup and any exclusions. A subscription price alone does not describe the migration work or ongoing service.

What to send in your first enquiry

Tell us your current platform, approximate users, what needs moving, the main business problem, locations and preferred timing. Say whether you need a migration project, ongoing Microsoft 365 support or both. An outline is enough to start; the assessment establishes feasibility, responsibilities and costs.