Google Workspace to Microsoft 365: how to move your business email

Three ways to move Workspace mail to Microsoft 365

Here is the short version:

Option 1: Microsoft’s built-in Google Workspace migration

Exchange Online has a migration feature built for exactly this move. In the Exchange admin center, under Migration, an admin creates a migration batch, chooses Google Workspace as the source and supplies a CSV file listing the users to move. According to Microsoft, it can transfer mail, rules, calendars and contacts. Microsoft offers an automated version, which does several of the required Google-side setup tasks for you, a manual version and PowerShell; it recommends the automated one.

How it works in practice

• Preparation. You verify your domain in Microsoft 365, create two routing subdomains (one pointing to Microsoft 365, one to Google) and provision each person as a mail user in Microsoft 365 before their batch starts. The Google admin running the migration needs specific project and service account roles.
• Batches. You can move everyone at once or in stages. Mail keeps syncing from Google until you complete the batch, and migrated users’ new mail is forwarded to Microsoft 365 through the routing domain.
• Licences. When a batch starts, mail users are converted to mailboxes. Microsoft’s instructions say to assign the Exchange license after that point.
• Cutover. When all batches are done, you point your domain’s MX record at Microsoft 365 yourself.

Known limits

Microsoft documents a few things that don’t come across: vacation and automatic-reply settings, room bookings, shared calendars and event colors, and some contact details (only three email addresses per contact are migrated). Migrated rules arrive switched off so users can check them first. The largest single message that migrates depends on your tenant’s message size limit, 35 MB by default and configurable up to 150 MB. Microsoft also strongly recommends turning off retention (MRM) and archiving policies during the migration, because they make moved items look “missing” in verification checks.

For live mailboxes, with admins who can access both consoles, this is often the best choice. Microsoft’s steps and screens change from time to time, so follow the current Microsoft Learn article for the Google Workspace migration rather than an old screenshot.

Option 2: Third-party migration tools

A number of commercial services specialize in tenant-to-tenant moves. They connect to Google Workspace and Microsoft 365 with admin consent and copy data on a schedule, usually with dashboards, per-user reports and retries for items that fail.

They make sense when the project is bigger than mail, such as shared drives, many domains or a partner-led cutover. They cost money, usually per user or per gigabyte, and what they copy varies, so compare their lists of supported and unsupported items with what your team actually uses before you buy. For a small business with simple mailboxes, Microsoft’s built-in migration often does the same mail job at no extra cost.

Option 3: Export to MBOX, convert to PST, import

The third route doesn’t connect the two systems at all. You export the mail from Google as MBOX files, convert them to Outlook PST files, and import those into Microsoft 365. It is a one-time snapshot, not a sync, which is exactly why it suits mailboxes that no longer change.

Step 1: Get the MBOX

• Google Takeout, for an account someone can still sign in to. Selecting only Mail gives you one MBOX file with every message’s labels recorded inside. Workspace admins can turn Takeout off for users, so check that first. Our Takeout guide walks through every screen, and common Takeout problems covers the usual hiccups.
• Google Vault, for admins on an edition that includes Vault. Vault can export Gmail as MBOX or PST, without signing in as the user. Export files are available for 15 days after you start the export, and large MBOX exports are split into several ZIP files.

Step 2: Convert MBOX to PST

If Vault already gave you PST files, skip this. Otherwise, you need a converter, because Outlook and Microsoft 365 import PST, not MBOX. Our comparison of four MBOX to PST methods covers free and paid options. MoveMyInbox is one: upload the MBOX in your browser, choose the Gmail labels folder mode, and download a Unicode PST where labels become folders and attachments and read and flagged status are kept. One conversion handles up to 50 GB, and you see the price on the pricing page before paying.

Step 3: Import into Microsoft 365

• Through Outlook, one mailbox at a time: sign in to the user’s Microsoft 365 mailbox in classic Outlook and use File → Open & Export → Import/Export. The PST import guide has the details, and importing PST in the new Outlook covers the newer app.
• With the Microsoft Purview PST import service, for many files: an admin uploads PSTs with Microsoft’s AzCopy tool, maps each file to a mailbox (or archive mailbox) in a CSV file, then starts an import job in the Purview portal. Microsoft recommends keeping each PST at 20 GB or less for this service, and notes that imports turn on a retention hold for the mailbox, which you can switch off later.

Which option fits your situation?

Mixing methods is normal. A common pattern is to move active people with Microsoft’s tool and handle departed users and old archives with exports, so the main batches stay small and fast.

Planning checklist

DNS and the MX cutover

• Lower the TTL on your MX record a day or two in advance so the change spreads quickly when you make it.
• Switch MX to Microsoft 365 only once mailboxes are ready, ideally at a quiet time such as a Friday evening. Mail already in flight may still arrive at Google for a while, so keep the Google mailboxes until a final sync or export has picked it up.
• Update SPF, and set up DKIM and DMARC for Microsoft 365, so your outgoing mail isn’t marked as spam.

Labels become folders

Outlook uses folders, not labels. Whatever the method, labels end up as folders, and how a message with several labels is handled depends on the tool: some copy it into each folder, others put it in one. Tell users what to expect, and check a heavily labelled mailbox during the pilot. See how Gmail labels map to Outlook folders for the details.

Calendars and contacts

Microsoft’s built-in migration and many third-party tools move calendars and contacts. An MBOX export does not: it is mail only. If you use the export route, export contacts and calendars separately (Takeout offers them as their own products) and import them into Outlook, and remember that shared calendars, room bookings and meeting invitations sent to outside guests need manual attention.

Pilot first

• Migrate one or two willing users before everyone else, ideally including someone with a large mailbox.
• Compare folder counts, open old attachments, check calendar entries and test sending and receiving.
• Check phones, and time the pilot to estimate how long the full migration will take.

Everything else

Check that each Microsoft 365 mailbox has enough storage, and list shared mailboxes, groups and aliases, since they need their own plan.

After the cutover: archives and leftovers

Don’t cancel Google Workspace the week mail starts flowing into Microsoft 365. Keep it a while, and do these last jobs first:

1. Export any mailboxes that weren’t migrated, including suspended and archived users, with Vault or Takeout.
2. Keep a copy of every export, MBOX or PST, in your own storage, separate from both cloud services.
3. Confirm with whoever handles legal and finance how long you must keep old email before deleting anything.
4. Remove the temporary routing subdomains and aliases once everything is done, as Microsoft’s guide notes.

For a step-by-step look at saving a whole account before it closes, see how to archive an email account before closing it.

Frequently asked questions