How to move your business to Microsoft 365 without losing email

This guide is for a small business moving from old email, a local server or a mix of personal accounts and shared folders into Microsoft 365. It explains the practical order of work so email continues to arrive and people can find their files. A migration is not just buying licences: it is an organised move of identities, data, settings and working habits.

Step 1: audit what you have before buying anything

Start with a list of every person, mailbox, shared mailbox, mailing list, device and file location. Include former staff accounts that still receive customer emails, generic addresses such as sales@, and folders kept on a desktop PC, server, USB stick or someone's personal cloud drive. Ask departments where the latest copy of each important document really lives. The answer is often less tidy than expected.

Record the essentials

• Users, aliases, shared mailboxes, groups and public-facing email addresses.
• Mailbox sizes, old archives and any legal or customer retention need.
• Files by owner, purpose, location and who needs access.
• Domains, registrar access, current DNS records and email service logins.
• Phones, PCs and tablets that will need Outlook, Teams or OneDrive configured.

Step 2: choose licences for how people actually work

Choose plans after the audit, not from a feature list. Some people need desktop Office apps, a larger mailbox or advanced security; others only need email, Teams and browser-based documents. Include shared devices, seasonal staff and managers who need access from several devices. Licence names and included features change over time, so check the current details before ordering.

Step 3: prepare the tenant, security and DNS

DNS is the set of records that tells the internet where your domain's services live. MX records direct incoming email; other records help prove that legitimate mail from your domain should be trusted. You normally add verification records first, then update the MX and related records at cutover. A wrong DNS change can affect email, so keep a copy of existing records, know who can log in to the registrar and make changes in a planned window. Our guide to securing Microsoft 365 covers the controls worth having from the start.

Step 4: move mailboxes and shared email carefully

Set up users, licences and mailboxes in advance. Test a pilot mailbox with a willing member of staff and make sure they can send, receive, search old messages and use their signature. Create shared mailboxes and permissions before the main cutover. If email from a website or copier needs attention, test it with a temporary configuration rather than waiting for a customer to report that it has stopped.

A sensible email cutover sequence

• Copy existing email while the old system remains live.
• Check a pilot user and document any adjustments.
• Tell staff the cutover date, expected sign-in steps and support contact.
• Change MX and related DNS records at the agreed time.
• Run a final mail copy, then test internal and external delivery.

Step 5: organise files before moving them

Microsoft 365 can replace scattered folders, but only if you decide where shared work belongs. Personal work belongs in OneDrive. Department or project work belongs in a shared SharePoint or Teams site with named owners and sensible permissions. Do not simply copy every old drive, USB stick and desktop folder into one huge library. Remove duplicates, agree a clear folder structure and archive material nobody needs every day.

Step 6: make day one easy for staff

Staff do not need a technical lecture. They need to know when to sign in, where their email is, where shared files have gone, how to use multi-factor authentication and who to call for help. A migration is the natural moment to set people up with a passkey rather than text-message codes, because everyone is signing in fresh anyway; our Microsoft 365 passkey rollout guide covers the settings. Send a short checklist in advance and have someone available during the first morning. Install Outlook, Teams and OneDrive on managed PCs ahead of time where possible; for personal devices, give clear instructions and keep work data separate.

Step 7: tidy up after the move

Once everyone is settled, remove access to the old mail system only when you have agreed what to retain. Cancel unused subscriptions, update documentation, review admin roles and check that backup covers the new Microsoft 365 data. A cloud service does not remove the need for recovery planning. Read our business data backup guide before assuming deleted mail or files will always be recoverable, and make sure users know how to get day-to-day IT support.

Finally, review the project with the people who use the system. Note what made work easier, which folders still need sorting and what training would help. That turns a migration into a better way of working rather than a new badge on the same old mess.

What to do next

Make the audit list first, then plan the pilot and DNS cutover around your business calendar. TSS helps organisations in Bury, Greater Manchester and Lancashire move email and files with a clear handover. Arrange a free, no-obligation chat if you want a second pair of eyes on your current setup.