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How-to · Google Workspace

Install and run Google Workspace Migration for Microsoft Outlook (GWMMO)

At the end, the email, calendar and personal contacts from an Outlook profile or PST file on a Windows PC are imported into a Google Workspace account, with a log of anything that failed.

Updated 10 steps8 official sources
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Before you start

What you need before step 1

Applies to: Google Workspace Migration for Microsoft Outlook (GWMMO) on Windows with desktop Outlook, as documented by Google

Admin roles you need

  • The person running GWMMO signs in with the target Google Workspace account (users can run it themselves).
  • A Google Workspace administrator must create the target accounts first (see Bulk create users in Google Workspace).
  • A local administrator on the PC to install it, or an IT team to push the MSI with software deployment tools.

Licences

  • Each target user has a Google Workspace licence with Gmail turned on.

Reference documentation

Google Workspace Migration for Microsoft Outlook (download page)Choose the EXE (Recommended for users) or MSI (Recommended for admins), 32-bit or 64-bit to match Outlookhttps://tools.google.com/dlpage/gsmmoRead
GWMMO MSI for admins, 32-bit OutlookDirect MSI link from Google's download page, for deployment toolshttps://dl.google.com/outlookmigration/enterprise_outlookmigration.msiRead
GWMMO MSI for admins, 64-bit OutlookDirect MSI link from Google's download page, for deployment toolshttps://dl.google.com/dl/outlookmigration/x64/enterprise_outlookmigration.msiRead
Google help: About GWMMO (system requirements)Reference: supported Windows and Outlook versionshttps://knowledge.workspace.google.com/admin/migrate/about-gwmmoRead

Also have ready

  • Windows: Google lists 32-bit and 64-bit Windows Vista, 7, 8, 10 and 11 (generally available releases with the latest patches). macOS, Windows XP and Windows Server 2003 are not supported.
  • Outlook: desktop Outlook 2003 SP3, 2007 SP2, and 32-bit or 64-bit Outlook 2010, 2013, 2016, 2019, 2021, 2024 or the Microsoft 365 desktop app. Outlook on the web, Outlook for Mac, mobile Outlook, Outlook from the Microsoft Store and 64-bit Office on Arm devices are not supported.
  • Install the latest Outlook and Windows updates first, and sign in to the Google Workspace account once in a browser to accept Google's terms.
  • PST files on a local drive (not a network share), with read and write access for the user. Google says read-only PST files cannot be imported.
  • Admins: Google recommends turning on smart features and personalisation at least 24 hours before migrating if users need to search attachments in imported mail.
Step by step

10 steps

  1. 1

    Check which Outlook you have

    Where: Outlook on the Windows PC: File > Office Account > About Outlook

    Note whether Outlook is 32-bit or 64-bit (shown at the top of the About window). You need the matching GWMMO edition if you use the MSI. Then close Outlook completely.

    You should see: You know the bitness, and Outlook is closed.
  2. 2

    Download GWMMO

    Where: Microsoft Edge or another browser on the Windows PC

    Go to https://tools.google.com/dlpage/gsmmo. For one PC, download the Recommended for users EXE. For many PCs, IT downloads the Recommended for admins MSI in the 32-bit or 64-bit edition that matches Outlook and deploys it with their software deployment tool.

    You should see: The installer file is in your Downloads folder.
  3. 3

    Install it

    Where: Windows PC with Outlook closed

    EXE: double-click the downloaded file and follow the installer. Admin-prepared install: open Start > Microsoft System Center > Software Center > Applications > Google Workspace Migration for Microsoft Outlook > Install. Install only one copy of GWMMO per user.

    You should see: The installer finishes without errors.
  4. 4

    Start GWMMO

    Where: Windows Start menu

    Open Start > Google Workspace Migration > Google Workspace Migration for Microsoft Outlook. Run only one instance at a time.

    You should see: The GWMMO wizard opens and asks for your account details.
  5. 5

    Sign in to Google Workspace

    Where: GWMMO wizard > Enter your account details

    Enter your Google Workspace email address. Under password, choose Yes, I have a password if you sign in to Google with a Google password, or No, help me sign in if your organisation uses single sign-on. Tick Remember me only if you will run more imports from the command line. Select Next and complete the Google sign-in that follows.

    You should see: The wizard moves on to choosing what Outlook data to import.
  6. 6

    Choose an Outlook profile or PST file

    Where: GWMMO wizard > Choose what Outlook data to import

    To import from Outlook directly, choose your Outlook profile name; GWMMO copies the data the profile holds right now. To import a PST, choose From PST File(s) and browse to the file; Ctrl-click to select several. The PST must be on a local drive.

    You should see: Your profile or PST file names are shown as the source.
  7. 7

    Choose migration options

    Where: GWMMO wizard, same page

    Select Migrate all data for the first import. Google warns this duplicates contacts and overwrites calendar data if the Google account already has data (email is not duplicated). Select Migrate only new data to resume an interrupted import or pick up mail that arrived since the last run. Select Next.

    You should see: The wizard shows the data selection page.
  8. 8

    Pick the data and start

    Where: GWMMO wizard > data selection page

    Choose what to import: email, calendar and contacts, all at once or one at a time. Google documents options to exclude junk and deleted email and to import only mail sent before or after a date. Then start the migration.

    You should see: A progress screen showing the number of items migrated and the number remaining.
  9. 9

    Watch the import

    Where: GWMMO progress screen

    Google imports contacts first, then calendar, then email; several PST files go one after another. Large mailboxes can take several hours and you can use Google Workspace meanwhile. Use Pause Migration and Resume Migration if needed. Select the Migration log file link to see errors. If you close the wizard or restart the PC, run it again and choose Migrate only new data.

    You should see: The counter reaches zero items remaining.
  10. 10

    Finish and check Gmail

    Where: GWMMO wizard, then Gmail in a browser (mail.google.com)

    Select Start new migration to import more data in stages, or Cancel to close the wizard. Sign in to Gmail: Outlook folders appear as labels, flagged messages as starred, deleted items in Trash and junk in Spam. Tasks, notes, journal entries, rules and signatures are not imported.

    You should see: Your mail is under labels named after your Outlook folders, with events in Google Calendar and contacts in Google Contacts.
From experience

Expert tips

Read the trace file first

Trace logs are in C:\Users\<user>\AppData\Local\Google\Google Apps Migration\Tracing\ClientMigration, one per run, named by date and time. Search for lines at level E (error) or F (fatal); for network or TLS problems the log shows the IP address it tried and the certificate details.

Rerun with Migrate only new data after an interruption

If the wizard stays open through a dropped connection, Google says it resumes where it left off. If you had to close it or restart the computer, run it again and select Migrate only new data to avoid duplicate contacts.

Check the Outlook build before you visit the user

GWMMO needs classic desktop Outlook (Microsoft 365 desktop app, 2016, 2019, 2021 or 2024). Outlook from the Microsoft Store, Outlook on the web and Outlook for Mac are not supported, and nor is 64-bit Office on ARM devices.

Rescue mail from Deleted Items and Junk first

GWMMO does not migrate junk mail or deleted items. Ask users to move anything they need out of those folders before the run.

Copy PST files to a local disk

Close Outlook and copy the PST to the local drive before importing. A PST that is open in another program, read-only or on an unreachable path causes the 0x80040109, 0x8004010f and 0x80070035 errors.

Use the command-line version for admin-run migrations

Admins can run GWMMO from the command line for a single user, which also allows excluding specific mail folders. See Google's Run migrations from the command line.

Check it worked

How to confirm it worked

  • In Gmail, compare the message count of a few labels with the same Outlook folders.

  • Google Calendar shows past and future events from the default Outlook calendar, and Google Contacts shows your personal contacts.

  • The log files in C:\Users\yourname\AppData\Local\Google\Google Apps Migration\Tracing\ClientMigration show no failed items, or only ones you expect (for example messages over 25 MB).

Undo

How to reverse it

Rollback:

An import cannot be undone by GWMMO; imported mail, events and contacts stay in the Google account until you delete them yourself in Gmail, Calendar and Contacts. Your Outlook profile and PST files are not changed. To remove the program, uninstall Google Workspace Migration for Microsoft Outlook from Windows Settings > Apps.

Troubleshooting

Errors you might see

User has not agreed to the Gmail Terms of Service

Cause: The user has never signed in to Gmail and accepted the terms.

Fix: Sign in to Gmail in a browser, accept the terms, then run GWMMO again.

The version of the app you're using doesn't include the latest security features to keep you protected (Error 400: invalid_request)

Cause: An old GWMMO version is rejected at sign-in.

Fix: Download and install the latest version from tools.google.com/dlpage/gsmmo.

Another process is accessing the PST file being migrated or the Outlook profile at the same time as GWMMO. (0x80040109)

Cause: Outlook or another program has the PST or profile open.

Fix: Close other MAPI programs and exclude PST files from antivirus, backup and desktop search scans.

GWMMO requires both read and write access to the file. (0x8004010f / 0x80070005)

Cause: The PST is read-only or the user lacks permission.

Fix: Give the user read and write permission on the PST file.

The PST file that is being migrated has an incorrect path. (0x80070035)

Cause: The PST is on a network share.

Fix: Copy the PST to a local drive and import it from there.

GWMMO is experiencing temporary errors. (0x80072ee2)

Cause: A transient failure, such as a network timeout.

Fix: Run again with Migrate only new data. Google also documents registry values to extend the connection timeouts.

FAQ

Questions

Does GWMMO run on a Mac?

No. Google lists macOS as not supported, along with Outlook for Mac and Outlook on the web.

What does GWMMO not migrate?

Tasks, notes, journal entries, RSS feeds, rules and signatures. Messages over 25 MB with attachments, or with file types Gmail blocks, are skipped. Contact folders are not kept.

Can I run it again later?

Yes. Choose Migrate only new data to add mail that arrived since the last import without duplicating contacts or overwriting calendar data.

Is there a version for admins to migrate for users?

Google provides a command-line version that admins can run for a single user; see Run migrations from the command line.

Sources

Official sources

Vendors change menus and requirements. Confirm on the source before you rely on a detail. Last checked 4 Nov 2026.

Google: Download Google Workspace Migration for Microsoft OutlookGoogle Workspace Admin Help: About GWMMOGoogle Workspace Admin Help: Set up GWMMO (for admins)Google Workspace Learning Center: 1. Download & install GWMMOGoogle Workspace Learning Center: 2. Sign in & set up Google WorkspaceGoogle Workspace Learning Center: 3. Choose what Outlook data to importGoogle Workspace Learning Center: 5. Monitor your migrationGoogle Workspace Admin Help: GWMMO error codes & messages