How to migrate to Microsoft 365
In this guide & where to go next
Part of the Microsoft 365 for Business series. Related: Microsoft 365 Vs Google WorkspaceMicrosoft 365 Business Plans Compared
Want it handled? IT Cares — hands-on managed IT across Canada.
To migrate to Microsoft 365, you verify your domain in the admin centre, create user accounts and licences, then move existing email, contacts, calendars and files from your old system using migration tools or a cutover/hybrid method. The goal is to transfer everything without losing data or interrupting email flow, then update DNS records to point mail to Microsoft and confirm users can sign in and work normally.
Plan before you move anything
A smooth migration starts with discovery, not data transfer. Before touching mailboxes, document what you have:
- How many mailboxes and how much data exists, and where it currently lives (an on-premise server, Google Workspace, a hosting provider, or another tenant).
- Which files, shared drives and calendars need to come along.
- Your DNS provider and who controls the domain records.
- Any line-of-business apps, scanners or printers that send email and will need reconfiguring.
This inventory determines the migration method and the timeline. Skipping it is the most common cause of dropped email and missing files. For Canadian businesses, this is also the point to confirm data residency settings and how the move affects PIPEDA and Law 25 obligations.
Choosing the right migration method
The method depends on your source system and size:
- Cutover migration — move all mailboxes at once over a weekend. Simple and ideal for small businesses with a few dozen users.
- Staged or hybrid migration — move users in batches while keeping old and new systems running together. Best for larger Exchange environments that cannot tolerate downtime.
- IMAP or third-party tools — used when migrating from Google Workspace, hosted email, or non-Microsoft systems.
File data in shared drives moves to OneDrive and SharePoint, which usually needs a tool to preserve folder structure and permissions. Matching the method to your environment is what keeps the project predictable and avoids surprises mid-migration.
Executing the cutover with no lost mail
The riskiest moment is the DNS cutover, when email starts flowing to Microsoft instead of your old system. Done carefully, no message is lost:
- Pre-stage all mailbox data so existing mail is already in Microsoft 365 before the switch.
- Lower the DNS TTL in advance so the change propagates quickly.
- Update the MX, autodiscover and SPF/DKIM records at the planned time, ideally outside business hours.
- Run both systems in parallel briefly to catch any messages in transit.
After cutover, configure Outlook profiles, reconnect mobile devices, and verify that printers, scanners and any apps that send email still work. A short overlap window ensures nothing falls through the cracks during propagation.
Securing and finishing the migration
Migration is not finished when email arrives — it is finished when the tenant is secured and users are productive. The closing steps include:
- Enforcing multi-factor authentication on every account before it is exposed to the internet.
- Configuring OneDrive backup so files sync to the cloud, and adding third-party backup for email and documents.
- Setting up SharePoint sites and permissions to replace old shared drives.
- Decommissioning the old server or licences once data is verified.
For Canadian organizations, this is also when retention and audit policies are set to satisfy Law 25 and PIPEDA. A managed migration handles all of this in sequence so staff experience a clean handover rather than weeks of email problems and missing files.
FAQ
How long does a Microsoft 365 migration take?
A small-business cutover migration of a few dozen mailboxes is often completed over a single weekend, with users back to normal on Monday. Larger or hybrid migrations run in batches over days or weeks. The actual mailbox transfer time depends on total data volume and internet speed, while planning and configuration usually take longer than the data move itself.
Will I lose any emails during the migration?
Not with proper planning. By pre-staging mailbox data before the DNS cutover and running both systems in parallel briefly, no message is lost. The risk comes from rushed, unplanned switches. A staged cutover with lowered DNS TTL and a short overlap window ensures messages in transit during the change are still delivered.
Can I migrate from Google Workspace to Microsoft 365?
Yes. Email, contacts, calendars and Google Drive files can all be migrated to Microsoft 365 using migration tools designed for Google Workspace. The process maps Google data to Exchange Online, OneDrive and SharePoint. Careful sequencing of the cutover keeps mail flowing, and most small-business moves complete over a weekend.
Do I need to keep my old email server running after migration?
Only briefly. Keep the old system live during a short overlap window to catch any in-transit messages and to verify all data transferred correctly. Once you confirm mailboxes, files and calendars are complete in Microsoft 365, the old server or hosting can be safely decommissioned, ending those licensing and maintenance costs.