Microsoft 365 Migration Checklist for Small Businesses

A Microsoft 365 migration moves your business email, calendars, contacts and files from where they live now, such as Google Workspace, a web host’s email, an office Exchange server or a shared drive, into Exchange Online, OneDrive, SharePoint and Teams. Much of the work is preparation: the right licences, access to your DNS, security settings and a clear plan for the moment mail starts arriving in the new system.

Microsoft’s own tools handle the common routes, and its estimates put the median time for a mailbox under 50 GB at one to two days. This checklist covers each stage in order, using Microsoft’s published limits and figures, so you can plan the move or check a provider’s proposal.

What a Microsoft 365 migration involves

Most small-business moves follow one of five routes, each with its own Microsoft tool and limits.

Migration Manager also moves content from Box, Dropbox and Egnyte. If you still run Exchange Server 2016 or 2019, note that Microsoft ended support for both on October 14, 2025, so they no longer get security fixes; Microsoft’s options are Microsoft 365 or Exchange Server Subscription Edition.

Choosing Microsoft 365 licences

The standard versions of all three business plans include business email, 1 TB of OneDrive storage per user and Teams, and together they’re capped at 300 users. The differences are the apps and the security tools.

Microsoft also sells versions without Teams or with Copilot, and prices change, so confirm before you buy. You don’t have to put everyone on the same plan, but Business Premium’s security and management benefits only apply to users with devices managed under it, and Microsoft recommends deploying it to all users if you choose it. Shared mailboxes such as info@ need no licence up to 50 GB, and admin-only accounts need none either.

Before you migrate: inventory, DNS and clean-up

Take an inventory

• Mail: every user mailbox with its size, plus shared mailboxes, room and equipment calendars, distribution lists and aliases.
• Files: each shared drive or folder, who can open or change it, and roughly how much it holds.
• Devices and apps: computers and phones to set up, and any scanner, printer or software that sends email.

Confirm DNS and domain access

Make sure you can sign in to the registrar or DNS host for every domain you send email from. You’ll add a TXT record to verify each domain in Microsoft 365, then later change the MX, Autodiscover and SPF records. If your old provider also hosts your DNS, sort out access now rather than on cutover night.

Clean up and communicate

Delete or archive what nobody needs, and shorten deeply nested folders, because SharePoint and OneDrive allow at most 400 characters for the full path, including the file name. Microsoft also recommends turning off retention and archiving policies on the new mailboxes until migration finishes, since items they move or delete can be reported as missing. Then tell staff what will change and when: Microsoft’s own cutover process starts with that notice and ends with a welcome message explaining how to sign in.

Set a security baseline before cutover

Put sign-in security in place before mailboxes go live.

• Security defaults or Conditional Access. Security defaults cost nothing and are on by default in new tenants. They make every user register for multifactor authentication (MFA), require MFA for admins and block legacy authentication. Conditional Access lets you write your own rules instead but needs Microsoft Entra ID P1, which Business Premium includes; if you use it, you switch security defaults off and replace them with policies.
• Separate admin accounts. Microsoft recommends doing daily work from an ordinary account, keeping admin accounts few, giving each the least-privileged role that does the job and keeping at least two emergency access accounts that aren’t assigned to one person. Microsoft began enforcing MFA for the Microsoft 365 admin centre in February 2025.
• Devices that send email. Legacy authentication includes older mail protocols, so a scanner or app that sends mail with just a username and password can stop working. Microsoft plans to disable Basic authentication for SMTP AUTH by default in existing tenants at the end of December 2026, so plan a supported method now.

For the wider set of controls, see our small business cybersecurity checklist.

Cutover methods, DNS changes and timing

Cutover, express or staged

A cutover migration moves every Exchange mailbox in one batch, typically over a few days, and Microsoft suggests it for 150 mailboxes or fewer. Express migration (minimal hybrid) moves Exchange 2010, 2013 or 2016 mailboxes over a couple of weeks or less. Staged migrations move batches of users over a few weeks or months, and full hybrid lets you move users gradually while both systems stay connected. IMAP and Google Workspace migrations keep syncing new mail until you complete them. Start with a small test group; Microsoft’s express migration guidance suggests two or three users.

DNS changes, in order

1. Before the migration starts, lower the TTL on your MX records to 3,600 seconds (one hour) or less.
2. Create users and mailboxes and start syncing data before you touch the MX record.
3. Point the MX record to the value in the Microsoft 365 admin centre, and remove the old MX records or give them a lower priority.
4. Add the Autodiscover CNAME so Outlook and phones find the new mailboxes, and merge Microsoft 365 into your existing SPF record so there’s still only one. Then set up DKIM and DMARC.
5. Wait. Other mail systems can take up to 72 hours to see the new MX record. For a cutover, confirm a sync has run since mail started arriving directly before you delete the migration batch.

Timing and speed

Migrations often run after hours, Microsoft notes, when they can collide with backup jobs on your own servers. Speed depends on the source too: Google limits how much data can be pulled in a given period, and IMAP and simple Exchange migrations move 20 mailboxes at a time by default.

After the move: devices, Teams and backup

Outlook, phones and shared mailboxes

With Autodiscover pointing to Microsoft 365, Outlook and mobile mail apps can find each mailbox, though Outlook may need a new profile after a cutover. Check versions as well: Office and Outlook 2016 and 2019 reached end of support on October 14, 2025, and Business Standard and Premium include the current desktop apps. Test every shared mailbox; each person who opens one needs an Exchange Online licence of their own.

Teams and SharePoint structure

Plan teams around who works together and who should see what, because each team comes with a Microsoft 365 group and a SharePoint site. Standard channels store files in that site, each private or shared channel gets its own site, and files shared in chats are stored in OneDrive. Known Folder Move puts users’ Desktop, Documents and Pictures folders in OneDrive; Microsoft recommends syncing no more than 300,000 files across all the libraries a person syncs.

Decommission carefully

Keep the old service until mail flow is confirmed and final syncs are done; once a cutover batch is deleted, mail still reaching the old server isn’t copied across. Then tidy DNS and cancel the old subscription. Before removing an Exchange server, read Microsoft’s decommissioning guidance: it recommends contacting Microsoft Support first, and organizations that keep syncing accounts from on-premises Active Directory have extra steps.

Retention isn’t the same as backup

Microsoft 365 keeps deleted data for fixed periods. Permanently deleted mail stays recoverable for 14 days by default, adjustable up to 30. SharePoint and OneDrive recycle bins hold items for 93 days, and Files Restore can roll a library back to any point in the last 30 days. Microsoft says its lagged mailbox database copies aren’t meant for recovering individual mailboxes or items, and it sells Microsoft 365 Backup as a separate pay-as-you-go product with recovery windows of up to two years. Decide how far back you need to restore, then pick a backup that reaches that far. Backup planning is part of our cybersecurity service.

What affects migration timeline and cost

There’s no standard price or schedule for a cloud migration; both scale with what you’re moving and how tidy it is.

Timeline

• Data volume and shape: Microsoft notes that a 4 GB mailbox of 400 items with 10 MB attachments migrates faster than a 4 GB mailbox of 100,000 smaller items.
• Method: a few days for a cutover, a couple of weeks or less for express migration, weeks or months for staged moves.
• Source and network: throttling at the source, and your upload capacity when data leaves an office server.
• Lead times: lowering DNS TTLs, the up-to-72-hour MX change, device setup and staff training.

Cost

• Licences: the ongoing cost, from the plan table above, multiplied by users.
• Tools: the SharePoint Migration Tool is free, cross-tenant moves need a one-time licence per user, and sources Microsoft’s methods don’t cover may need a partner or third-party software.
• Labour: planning, clean-up, running and checking batches, fixing errors, setting up computers and phones, and supporting staff in the first days.
• Related upgrades: replacing unsupported Office versions or computers, and adding backup.

When you compare quotes, check that each states the mailboxes, data volume, method, DNS work, device setup and after-migration support it assumes. For the ongoing side, see our managed IT services cost guide.

The printable migration checklist

If you’d rather hand off the work, YVR Technology plans and runs Microsoft 365 migrations for businesses across Greater Vancouver and the Fraser Valley. See our cloud services or contact us.