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Google Workspace to Microsoft 365
Your mail, files and calendars copied across and checked before anything is switched over, so the day it happens is quiet. Your email addresses do not change and nobody outside your business notices.
This page is mostly about what does not come across in an Office 365 migration, because that is the part nobody tells you until it is too late to plan around.
An Office 365 migration: what comes across, and what does not
Most of it comes across. The trouble is always in the handful of things that do not, and in the things that technically transfer but arrive looking different.
| What you have now | What happens to it | Worth knowing |
|---|---|---|
| Email in Gmail | Copied into your new Microsoft 365 mailbox | All of it, including attachments. Nothing is deleted from Google. |
| Gmail labels | Become Outlook folders | A message with three labels ends up in one folder, not three. See below, this is the one that surprises people. |
| Google Calendar | Comes across, including repeating events | Meeting rooms and shared resources are usually quicker to set up fresh than to migrate. |
| Google Contacts | Come across | Contacts you saved. The auto-collected "other contacts" list is rarely worth bringing. |
| My Drive files | Copied to OneDrive | Files still owned by someone who has left need an owner assigned first, or they are simply not there to copy. |
| Shared drives | Copied to SharePoint document libraries | The files move. Who can see them does not map across neatly, which is the hardest part of this migration. |
| Docs, Sheets and Slides | Converted to Word, Excel and PowerPoint | Ordinary files convert cleanly. Anything built on Apps Script, an add-on, or a Google-only formula stops working. |
| Google Groups | Recreated as distribution lists or Microsoft 365 Groups | Membership is recreated. The archive of past group conversations does not come across. |
| Google Chat and Spaces | Does not transfer | There is no supported path into Teams. Export anything that matters before you close the account. |
| Sites, Keep and Forms | Do not transfer | Rebuild them, or export and keep the export. Usually there is less here than people expect. |
| Google Vault holds and archives | Do not transfer | If you are under any legal hold, export before anything is cancelled. This one is not recoverable later. |
The labels thing, because it catches nearly everyone
Gmail lets one email carry several labels at once. An invoice can be tagged Accounts, Q3 and Smith Job, and it shows up under all three without anything being duplicated. Outlook does not work that way: a message lives in exactly one folder.
So a multi-labelled message has to be put somewhere, and it lands in one folder rather than three. If your business genuinely relies on cross-labelling, that gets discussed before the move, not discovered afterwards. Usually the answer is that Outlook search finds it regardless, and the labels mattered less than everyone assumed. Occasionally the answer is that a couple of workflows need rethinking, and it is much better to know that in week one.
What actually happens on the day
The copying is the slow part and it happens invisibly. The switch itself is short, and it is deliberately put on an evening or a weekend.
Before anything changes
Your Microsoft 365 tenant is built and your domain is verified, but mail delivery is untouched and still going to Google. Licences are assigned, a couple of pilot mailboxes are migrated and tested properly, and the setting that controls how quickly the internet notices a change (the TTL) is turned down in advance so the switch is quick when it comes.
The copy, which nobody notices
Mail, calendars and files copy across in the background over days or weeks depending on volume. Everyone keeps working in Google exactly as normal for the whole of this. There is no downtime and nothing to do differently.
The switch
The record that tells the world where to deliver your mail (the MX record) is repointed from Google to Microsoft. New mail starts arriving in Microsoft 365 within minutes for most senders and within a few hours for the rest. This is scheduled outside business hours.
Mail that was already in flight
Anything Google had already accepted still lands in Google. That is normal and it is planned for: a final catch-up pass sweeps those messages into Microsoft 365 afterwards, and forwarding stays in place as a second net. Some mail arrives a little late. None of it is lost.
What your staff see
They sign in to Outlook with their new details and their mail is there, oldest first, with the most recent items filling in over the following hours. Phones and tablets need the account removed and re-added, which takes a couple of minutes each and is worth doing together rather than one by one across a fortnight.
Which licence you land on
There are three sensible options for a business under 300 people. The difference between them is not really about features, it is about whether the security controls are included or bolted on later at a higher price.
Business Basic
Email, file storage and Teams, with Word and Excel in the browser only.
- No installed Office apps on the laptop
- Fine for shared or occasional accounts
- Usually a false economy for real staff
Business Standard
Everything in Basic, plus the installed Word, Excel, Outlook and PowerPoint people expect.
- What most businesses assume they are buying
- Security is the baseline only
- Add-ons later cost more than the step up
Business Premium
Everything in Standard, plus the Identity, email protection and device controls.
- Entra ID P1: sign-in rules that actually enforce MFA
- Defender for Office 365: links and attachments checked on click
- Intune: wipe a lost phone without wiping the person
Why Premium is usually the answer
Entra ID is Microsoft's Identity system, the thing that decides who gets to sign in and under what conditions. The P1 tier is what lets you say "require a second factor, but not from the office, and never from overseas" rather than just switching multi-factor authentication on and hoping. Without it, enforcement is blunt enough that people find ways around it.
Defender for Office 365 checks links at the moment someone clicks them rather than when the mail arrived, which is precisely how modern phishing gets past a filter. Bought separately and added to Standard, those two normally cost more than the gap between Standard and Premium, which is why Premium is usually the cheaper way to end up in the same place. Current pricing is confirmed at quoting rather than quoted here, because Microsoft changes it.
What to do with the Google side afterwards
Do not cancel it the following week. The cost of keeping it a little longer is trivial next to the cost of discovering something was left behind after it is gone.
The parts that are genuinely hard
This migration is well understood and it goes well, but it is not seamless and anyone telling you otherwise has not done many of them. Three things take real work, and knowing which three is most of the value.
Working out who should see what
Google and Microsoft think about sharing differently. Google hangs permission off the file and the shared drive; SharePoint hangs it off the library and the site, with inheritance underneath. There is no button that converts one into the other faithfully, and most shared drives have six years of ad-hoc sharing in them that nobody has reviewed. The honest approach is to decide who should have access, agree it with you, and build that, rather than reproduce an accident.
Everything you signed into with Google
Your accounting system, your CRM, the design tool, the booking system, the thing the receptionist set up in 2021. Anything using Sign in with Google is authenticating against an account that is about to change, and each one has to be found, re-pointed at Microsoft or moved to its own login, and tested. Nothing about this is technically difficult. It is simply a list, it is always longer than anyone expects, and it is the single most common reason a migration feels messy in week two. Building that list early is what stops it.
The spreadsheet that runs part of your business
Most businesses have one. It is held together with Apps Script, an add-on, or a formula that only exists in Google Sheets, and converting it to Excel breaks it. There is no clean fix, only a decision: rebuild it in Excel or Power Automate, replace it with something purpose-built, or keep that one file in Google and pay for a single account. All three are reasonable. Finding it the week after cutover is not.
Not sure this is the right move yet?
Plenty of businesses on Google Workspace are fine where they are, and being pushed towards Microsoft 365 by a head office, an accountant or a client requirement is not the same thing as needing to go. If the decision is still open, the useful conversation is about your situation rather than about the migration.
The questions everyone asks
Who runs it
Hamilton365 is Jamie Hamilton. Migrations are routine here rather than an event: more than 100TB of mailbox data moved into Exchange Online to date, and by day I run Identity and messaging infrastructure for one of Queensland's largest education providers, a 200,000-user environment. MCSE certified, 25+ years in the field.
The person who scopes your migration is the person who runs the cutover. Nothing is handed to somebody junior at the point where it matters, and there is nobody to be passed along to at 9pm on the night of the switch.
100TB+
Mailbox data migrated to Exchange Online
200,000+
Users managed across Microsoft Identity environments
25+ years
Enterprise IT experience
Request a migration plan
Tell me what you are running and what is worrying you. You get a plan and a fixed number, not a sales sequence.
Prefer to talk it through? Call 0403 401 250 or email jamie@hamilton365.com.au