A Microsoft 365 migration goes smoothly when the planning is done before anything moves. That means knowing exactly what you have, choosing how and when email will switch over, deciding where every file will land, and telling staff what will change. Whether you are leaving Google Workspace, merging two Microsoft 365 tenants, or retiring an on-premises Exchange or file server, the same planning steps apply.
Why planning matters more than the tools
Microsoft provides capable migration tools. What they cannot do is decide which mailboxes matter, who should own a shared folder, or whether Monday morning will start with missing email. Those are business decisions, and getting them wrong is what turns a migration into a week of disruption.
Common starting points
The planning steps
1. Inventory everything
List every user, shared mailbox, distribution list, calendar, file location and app that touches email. Note mailbox sizes and total file volume. Include the forgotten items: scanners that email documents, accounting software that sends invoices, and vendors who connect to your mail.
2. Settle licensing
Decide which Microsoft 365 plan each person needs before the move, and make sure licenses are available when mailboxes are created. Shared mailboxes and room calendars may not need a paid license, depending on size and features.
3. Plan identities
Decide what each person's username will be, whether accounts will sync from an on-premises directory, and how multi-factor sign-in (MFA) will be set up on day one. Changing usernames after a migration is disruptive, so settle naming early.
4. Plan the mail cutover and DNS
Your domain's mail exchanger (MX) record tells the world where to deliver your email. At cutover, it is changed to point to Microsoft 365. Microsoft notes that it can take up to 72 hours for other mail systems to recognize a changed MX record, so the old system should keep syncing for a few days afterward. Plan the change, and the related SPF, DKIM and DMARC records, for a quiet period.
5. Plan the data migration
Decide what moves and what does not. Old mailboxes of former staff, ten-year-old project folders and duplicate copies may be better archived than migrated. Check what each tool carries over. For example, Microsoft notes that Migration Manager copies only the latest version of each Google file by default and that file-level permissions are not migrated by default, and that IMAP-based mail migrations copy email but not calendars or contacts.
6. Communicate with users
Tell staff what will change, when, and what they need to do: sign in to the new account, set up MFA, reconnect phones, and where to find their files. A one-page guide and a short window for questions prevent most Monday-morning tickets.
7. Choose cutover weekend or staged
A cutover moves everyone at once, usually over a weekend. A staged migration moves people in batches. Microsoft's guidance for on-premises Exchange suggests a cutover is reasonable for fewer than about 150 mailboxes, with staged or hybrid approaches above that or when you want to move slowly.
8. Clean up after the move
Confirm mail flow and DNS, remove old forwarding, check that shared mailboxes and permissions work, retire the old system only after you have confirmed everything arrived, and cancel the old subscription. Set up backup for the new environment.
Cutover weekend or staged: how to decide
What drives cost and timeline
We do not quote migrations from a price list, because no two are alike. These are the factors that move the number:
A worked example
Take a hypothetical 12-person accounting firm on Google Workspace that also keeps client files on an aging office file server. The plan might move mail, calendars and contacts in one cutover weekend outside tax season, move the file server into SharePoint the following week after cleaning up old folders, and move Google Drive content last. Staff get a one-page guide on Friday and a check-in on Monday.
Common mistakes
How NexJen can help
If you want help with the plan itself, our Microsoft 365 consulting engagements are advisory: we review your environment and give you written recommendations and a roadmap. Migrations are separate project work, quoted at $200 per hour or as a fixed fee agreed in writing before work starts. Once you are on Microsoft 365, NexJen Essentials can take over day-to-day management, security and support.
Common questions
How long does a Microsoft 365 migration take?
It depends on users, data volume, sources and complexity. Small, single-source email moves are often planned around a single weekend; multi-source moves take longer.
Will we lose email during the cutover?
With planning, no. The old system keeps syncing while the MX record change spreads, which Microsoft says can take up to 72 hours.
Can we move Google Drive files too?
Yes. Microsoft's Migration Manager supports Google Drive, but check its defaults for permissions and file versions before you migrate.
Do you publish migration prices?
No. Every migration is quoted as a defined project because the cost depends on your specific environment.
Planning a move to Microsoft 365?
Tell us where your email and files live today. We can help you plan the migration and quote the work as a defined project.