Do we have to change our email addresses?

No. The domain moves from Microsoft to Google and addresses stay exactly as they are. Nobody outside the business notices anything except a change in message headers.

Will we lose any email?

No, provided the cutover is planned. Mail already accepted by Microsoft still lands in Microsoft, which is normal and expected; a catch-up pass sweeps those messages across afterwards and forwarding stays in place as a second net. Some mail arrives a little late. None of it is lost.

Can we run both platforms for a while?

Yes, and for a migration of any size you should. Split-domain routing lets mail be delivered to whichever platform holds each mailbox while people move across in batches. Free/busy calendar lookup between the two is workable but imperfect, so it is worth keeping the overlap short.

What happens to our Teams chat history?

It does not transfer. There is no supported path from Teams into Google Chat. Channel files can be moved because they live in SharePoint, but conversations and channel structure cannot. Export anything that matters before the tenant is closed.

Will our Excel files still work?

Ordinary spreadsheets convert cleanly, or can be kept in Excel format inside Google Drive. Anything carrying macros, Power Query or cross-workbook links does not survive conversion and needs a decision rather than a fix.

What about our Windows laptops?

This is usually the longest part. Devices joined to Entra and managed by Intune do not follow the identity to Google, and Google Workspace has no equivalent to Intune and Autopilot for Windows. Expect either a staged device rebuild or a period where the Microsoft tenant stays alive to manage the fleet.

How long does the whole thing take?

Mail and files copy in the background over days or weeks depending on volume, and the mail cutover itself is short and scheduled out of hours. The realistic timeline is set by the device fleet and by however many applications authenticate against Entra, not by the mailboxes.

Can Hamilton365 run this if we are moving to Google?

The Microsoft side of it, yes, and that is usually where the risk sits. Purview and legal hold exports, mailbox and file extraction, the application inventory, BitLocker escrow, clean domain removal and tenant decommissioning. The Google build itself is normally handled by the acquiring business’s own provider.

Microsoft 365 to Google Workspace Migration: What Doesn't Transfer

Most businesses asking about this are not choosing it. They have been acquired, or they have merged, and the other side runs Google Workspace. The acquirer’s platform usually wins, and the decision tends to arrive already made.

That changes what is useful to know. You are not weighing up features. You are working out what you are about to lose, and what has to be exported before somebody cancels the subscription.

This is the reverse of the migration most Australian businesses do. The mechanics look symmetrical and they are not. Microsoft 365 holds more things that have no Google equivalent at all, and the two that hurt most are compliance data and Windows device management.

Going the other way? Google Workspace to Microsoft 365 →

What comes across, and what does not

Most of it comes across. As always, the trouble is in the handful of things that do not.

What you have now	What happens to it	Worth knowing
Mailboxes in Exchange Online	Copied into Gmail	Mail, attachments and folder structure. Nothing is deleted from Microsoft.
Outlook folders	Become Gmail labels	Nested folders become nested labels. This direction is the easy one: one folder becomes one label, with none of the mess that goes the other way.
Outlook categories	Do not come across	The colour categories people use to triage. There is no field in Gmail for them to land in.
Inbox rules	Rebuilt as Gmail filters, by hand	Server-side rules can be listed and recreated. Rules created in the Outlook desktop client and stored locally are invisible until someone notices their mail has stopped sorting itself.
Shared mailboxes	No equivalent. Rebuilt as a Google Group or a licensed account	The one that costs money. See below.
Distribution lists	Become Google Groups	Membership is recreated. This part is straightforward.
Dynamic distribution groups	Do not come across	Rule-based membership needs Cloud Identity Premium, or the group becomes a manual list somebody has to maintain.
Room and equipment mailboxes	Recreated as Google calendar resources	Quicker to build fresh than to migrate. Bookings already sitting in them are a separate problem.
Calendars	Come across, including recurring events	Delegate permissions do not. Series organised by someone who has already left usually need rebuilding.
Contacts	Personal contacts come across	The address book itself rebuilds automatically from the Google directory.
OneDrive	Copied to Google Drive	Files come across. Sharing links people have already sent out stop working.
SharePoint document libraries	Copied to Shared Drives	The files move. Metadata columns, content types and most version history do not.
SharePoint lists	Do not come across	There is no Google equivalent. Anything built on top of one stops working with it.
Word, Excel and PowerPoint files	Kept as-is in Drive, or converted to Google formats	Ordinary documents are fine either way. Macros are not. See below.
Microsoft Teams	Does not transfer	Files live in SharePoint and can be moved. Channel structure, tabs and chat history cannot.
OneNote notebooks	Do not transfer	Google Keep is not a replacement. Export them while you can.
Power Automate, Power Apps, Power BI	Do not transfer	Anything automated in Power Platform is rebuilt or retired. There is no lift and shift.
Purview retention and eDiscovery	Do not transfer	Google Vault starts empty. Export before anything is cancelled. This one is not recoverable later.
Entra ID Conditional Access and MFA	Do not transfer	Policies are rebuilt in Google’s admin console under a different model, and everyone re-registers MFA.
Apps using Microsoft sign-in	Have to be re-pointed, one at a time	Every third-party system your staff sign into with their work account.
Intune-managed Windows devices	Does not transfer	The item that usually sets your timeline. See below.

The shared mailbox problem, which is really a budget problem

In Microsoft 365 a shared mailbox is free. accounts@, info@, support@, the one for the old trading name, 50GB each, no licence, as many as you like. Most businesses have more of them than they remember creating.

Google has no equivalent, and the two substitutes are not the same thing. A Google Group with collaborative inbox enabled is free, but it behaves like a mailing list with a shared queue bolted on rather than like a mailbox. A full user account behaves properly, but it costs a licence every month, for every shared address.

So the first task is to count them. Fifteen shared mailboxes is either fifteen new licences or fifteen workflows that have to change. Both are legitimate answers. Both are considerably cheaper to decide before the migration than after it.

The Excel file that runs part of your business

The same problem as the reverse direction, and more common. Where a Google business typically has one Sheet held together with Apps Script, a Microsoft business usually has several Excel files carrying macros, Power Query connections, or links into other workbooks.

Sheets does not run VBA. Power Query has no equivalent. A workbook that pulls from a database, refreshes itself and formats the result will open in Sheets and simply sit there.

Files can also be kept in their original Office format inside Google Drive and edited in Office. That keeps the file alive but not the automation, and it means part of your business still depends on Microsoft licences you were planning to cancel. The real choice is to rebuild it in Apps Script, replace it with something purpose-built, or keep a small number of Microsoft licences for the people who need them. All three are defensible. Finding the file in week two is not.

Windows devices, which usually set the timeline

This has no counterpart in the other direction, and it is the main reason these projects take longer than anyone budgets for.

If your laptops are Entra joined and managed with Intune, your identity, device enrolment, compliance policies, BitLocker recovery keys and sign-in are all the same system. Move the identity to Google and the devices do not follow. Google Workspace can manage Windows devices, but it is not Intune, there is no Autopilot equivalent, and machines that are already Entra joined generally have to be re-provisioned rather than re-pointed.

In practice that means either a device refresh running alongside the mail migration, or the Microsoft tenant staying alive purely to keep the fleet managed while it turns over. Both are normal. Neither takes a week.

BitLocker keys deserve their own sentence: if they are escrowed in Entra and the tenant goes away, they go with it. Export them before anything is cancelled.

Everything that signs in with Microsoft

Your accounting system, the CRM, the payroll portal, the industry tool the office manager set up in 2021. Where a Google business has a list of “Sign in with Google” apps, a Microsoft business usually has a longer one, because Entra is more often the corporate identity provider outright, frequently with SAML single sign-on properly configured rather than just a social login sitting on top.

Each one has to be found, re-pointed at Google or moved onto its own credentials, and tested. None of it is technically difficult. It is a list, it is always longer than anyone expects, and it is the single most common reason the second week feels messy.

The list already exists. Enterprise Applications in Entra shows what has been consented to and what is actually being used. Pull it early, while you still have the tenant to pull it from.

Compliance data, which is the only genuinely irreversible part

Everything else on this page can be redone slowly and badly if it has to be. This cannot.

If your organisation is under a legal hold, has retention policies configured in Purview, has ever run an eDiscovery case, or holds anything under a regulatory obligation, none of it transfers. Google Vault starts empty and begins retaining from the day it is switched on. Retention labels, litigation holds, audit log history and case data all live in the Microsoft tenant and stop existing when it does.

Export before anything is cancelled, not after. If there has ever been a dispute, an insurance claim or an employment matter, this is the first task of the project rather than the last.

How email investigation and eDiscovery exports work →

What to do with the Microsoft 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.

Keep it running, with nobody working in it, for at least 60 to 90 days. This is the window in which someone remembers a file, and it is the only reason that moment is survivable.

Take proper exports before you touch billing: mailboxes, OneDrive and SharePoint content, Purview and audit data, BitLocker recovery keys, and the Enterprise Applications inventory. Keep them somewhere that is itself backed up.

Check for legal holds before anything is deleted. If the organisation has ever been involved in a dispute or an insurance claim, this is not a formality.

Remove your domain from the Microsoft tenant properly rather than just cancelling the subscription. Google will not verify a domain that Microsoft still holds, and a half-removed domain causes odd mail routing problems months later that nobody connects back to this.

Then either cancel outright, or drop to a single low-tier licence holding an archive if you would rather keep something searchable.

If this is an acquisition, one thing worth saying

The platform decision is usually not yours. The export decisions are, and they run on a deadline somebody else controls.

The acquirer’s IT provider will run the Google side perfectly competently, and will have no particular interest in, or knowledge of, what is sitting in your Purview holds, your Entra app registrations or your BitLocker escrow. That part is yours to protect, and the window closes when the subscription does.

Microsoft 365 to Google Workspace: What Doesn’t Come Across