Last updated: 9 November 2026
Start with an audit of your users, devices, email, files and applications, then plan the structure, secure the Microsoft 365 tenant, migrate email and files, move or replace applications, train staff and retire the old server. For 10 to 50 people, email and files usually take a few weeks.
Signs it is time to move
Ageing server
Windows Server 2016 reaches the end of extended support on 12 January 2027. After that there are no more security updates.
People work from anywhere
Staff rely on a VPN, remote desktop or emailing files to themselves to work away from the office.
Files are scattered
Copies sit on laptops, USB sticks, personal Dropbox accounts and email attachments.
Backups are uncertain
Nobody is sure when the server was last backed up, or whether the backup would actually restore.
What moves where
| What | Where it goes | Replaces |
|---|---|---|
| Exchange Online | An on-site Exchange server or POP/IMAP email | |
| Shared files | SharePoint | The S: drive, organised by team or project |
| Personal files | OneDrive | My Documents and the desktop on each PC |
| Calls and chat | Teams | Meetings, chat and, if you want it, your phone system |
| Applications | Supplier’s cloud version or Azure | Software running on the office server |
Not everything has to move at once. Many businesses start with email and files, then tackle applications.
The migration plan, step by step
- Audit what you have: users, devices, email, file shares, applications, and who needs access to what.
- Plan the new structure: decide how SharePoint sites and Teams will be organised, and tidy permissions before anything moves.
- Secure the tenant first: turn on multi-factor authentication, set up conditional access and device management, and configure backup.
- Migrate email and check calendars, shared mailboxes and mobile devices.
- Migrate files to SharePoint and OneDrive, usually out of hours, with a final sync on switch-over day.
- Move or replace applications, working with each software supplier.
- Train staff and support them through the first few weeks.
- Decommission the old server securely, including wiping or destroying the disks.
Common mistakes to avoid
| Mistake | Why it matters |
|---|---|
| Copying the old mess across | Moving 20 years of folders unchanged into SharePoint just moves the problem. Clean up first. |
| Skipping multi-factor authentication | Stolen passwords are the most common way into Microsoft 365. Switch MFA on before the first mailbox moves. |
| Assuming Microsoft backs up your data | Under the shared responsibility model you are responsible for your data. A separate backup protects against deletion, ransomware and leavers. |
| Forgetting the broadband | Everything now depends on your internet connection, so check speed and consider a backup line. |
| Leaving the old server running | An unpatched server left on “just in case” is a security risk. Retire it once everything has moved. |
Is the cloud secure?
A well-configured Microsoft 365 tenant is usually far more secure than a server in a back office, and the key words are “well configured”. The NCSC cloud security guidance sets out 14 principles for choosing and using cloud services safely. Microsoft 365 is also covered by Cyber Essentials: cloud services you use are in scope, and you are responsible for configuring MFA, user access and security settings.
How ABCOM helps
As an NCSC Assured Service Provider (Cyber Advisor for Cyber Essentials) and a Sussex managed IT provider since 1996, we handle planning, migration and support in-house. We set up every tenant we migrate against those requirements and can give you a clear, costed migration plan covering what to move first and what to leave. See our managed IT services and the full guide, Moving to the Cloud: A Practical Guide for UK Small Businesses.
Quick answers
How long does a move to the cloud take?
For 10 to 50 users, moving email and files to Microsoft 365 usually takes a few weeks from audit to switch-over, with the cut-over done out of hours. Applications can take longer, depending on the supplier.
Will we still need a server in the office?
Most small businesses no longer need one once email and files are in Microsoft 365. Some specialist applications still need a server, which can often be hosted in Microsoft Azure instead.
Does Microsoft back up our Microsoft 365 data?
Microsoft keeps the service available, but you are responsible for your data under its shared responsibility model. We recommend a separate Microsoft 365 backup.
Thinking about moving to the cloud? Talk to us for a clear, costed plan.
Related answers and guides
- Moving to the Cloud: A Practical Guide for UK Small Businesses
- SharePoint Made Simple: A Small Business Guide
- ABCOM managed IT services
- Why do businesses fail Cyber Essentials?
- How often should we patch?
- All ABCOM FAQs
Sources and further reading
Related questions
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- Do you provide IT support near me in Sussex, Brighton, Crawley, East Grinstead and London?
- How do we decommission a server safely?
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- How do we change IT provider without losing access to our systems?
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