GWMMO release notes

Use these release notes to review improvements and new features in each version of Google Workspace Migration for Microsoft Outlook (GWMMO).

We recommend that you upgrade your version of GWMMO to In the near future, older versions of GWMMO will stop working.

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Release notes for

June 18, 2024

What's new
  • GWMMO now uses the latest, most secure, version of the installer. If you have an issue installing the previous version, try installing this version.

Release notes for

March 30, 2022

What's new
  • Best security practices implemented to help keep your account and data safe.

Release notes for

December 09, 2020

What's new
  • G Suite Migration for Microsoft Outlook is now Google Workspace Migration for Microsoft Outlook (GWMMO).

Release notes for

January 07, 2020

What's new
  • Improved detection of unsupported versions of Microsoft Office. If the installer detects an unsupported version of Office, it displays a clearer message with instructions to follow.
  • New OAuth endpoint used for exchanging authorization and access tokens. If you have a firewall, make sure the new endpoint is whitelisted:
    • Old endpoint:
    • New endpoint:
What's fixed
  • Fixed a confusing log warning about proxy auto detection failure. The message now explicitly states that proxy auto detection errors can be ignored if you're not using a proxy.

Release notes for

June 13, 2019

What's new
  • Improved error messaging when GSMMO is installed on an unsupported version of Windows.
  • Better handling of recurring events.
  • Enhanced diagnostics for newly-created labels.
  • Calendar events with rich-text format descriptions can be migrated.

    Note: Descriptions created in Outlook 2016 are converted to plain text.

What's fixed
  • Fixed multiple issues related to outdated timezone mappings.
  • Fixed an issue that produced unnecessary information in the logs. 
  • Fixed an issue that caused the sender's full name to not be displayed on event invitations.
  • Fixed an issue that caused valid profiles to not be displayed if there is a corrupted Outlook profile. 
  • Fixed an issue that caused the format of calendar event descriptions to break during migration.
  • Fixed an issue that caused calendar events to fail to migrate when the busy status was set to Working Elsewhere.
  • Fixed an issue that affected the way nested Gmail labels are created when the parent folder name conflicts with a special Gmail label.
  • GSMMO no longer tells Google Calendar to fan-out migrated events.
  • GSMMO no longer migrates Exchange folders if they are marked as hidden. 
  • Fixed an issue with migrating orphaned events (single instances of a recurring event).

Release notes for & earlier

Earlier version release notes

September 25, 2017

What's new
The logs contain more detailed network error messages, when connection failures occur.
What's fixed

Fixed issues where calendar exceptions to recurring events from an old G Suite Sync profile weren't being correctly migrated.

Fixed an issue where GSMMO was prevented from authorizing access to the Google Account when Microsoft Edge was set as the default browser.

Fixed an issue that caused GSMMO to fail at the start when a Click-To-Run edition of Outlook 2016 was installed, due to an internal error. The failure can also occur when trying to migrate data after creating a new G Suite Sync profile.

Fixed an issue that caused the truncation of MIME headers when reporting mail message migration errors in the trace log.

Fixed an issue with MAPI to MIME conversion that prevented messages being migrated if they had internationalized email addresses.

May 31, 2017

What's new

Google Apps Migration for Microsoft Outlook has a new name, G Suite Migration for Microsoft Outlook (GSMMO), and a new logo.

Better logging on enterprise MSI installer to help diagnose compatibility issues.

Better logging on Gmail label creation failures and labels cache refresh that helps with diagnosing email migration issues.

What's fixed

Fixed a crash that occurred in some cases when using a Click-To-Run edition of Outlook 2016.

Fixed several issues caused by Gmail label creation conflicts which prevented messages from being migrated, for example if the letter case is different ("Customers" in Outlook vs. "customers" in Gmail).

Fixed an issue which caused a server timeout error to be reported as a (local) network timeout.

Fixed an issue where Calendar exceptions to recurring events weren't being migrated for the invited user.

Fixed an issue where migration would fail if the username starts with a Windows reserved name and a period (for example, "").

Fixed an issue where GSMMO wouldn't refresh the OAuth token until it had expired (causing unnecessary retries and authentication error messages being written to the log) when using a Service Account.

Updated OAuth2 endpoints. See Troubleshoot network traffic issues to see if your firewall/proxy needs changes.

Fixed an issue that caused the migration to keep retrying in case of authorization issues instead of reporting failure to the user.

February 21, 2017

What's fixed

Fixed an issue where calendar exceptions to recurring events weren't being migrated for the invited users.

Fixed an issue where migrated email messages may include unexpected characters at the end of the email.

March 20, 2016

What's fixed

Fixed an issue where a message with an X500 sender address that couldn't be resolved to a valid SMTP address migrates with the From header of "unknown@domain."

Fixed an issue where messages failed to migrate to Gmail if they were in folders with leading or trailing spaces, or there were two or more consecutive embedded spaces in the folder name.

January 12, 2016

What's fixed

Fixed an issue where messages from a PST file containing invalid values in MAPI properties were converted to MIME messages with invalid From headers and then rejected by the Gmail API.

OAuth token is now refreshed before it expires, resulting in fewer 401 errors during large migrations.

Improved back-off behavior when the server returns an HTTP status 429 (Too Many Requests) response.

Message bodies are no longer written to the trace log when an email upload fails.

November 10, 2015

What's new

Added the quotaUser argument to all API requests to make sure the API quota is counted per user and not per IP.

What's fixed

Fixed an issue where messages were rejected by the Gmail API if the From header did not contain a valid SMTP address.

Failed API requests are now retried correctly using increasing intervals (exponential back-off).

October 25, 2015

What's fixed

Messages greater than 5Mb were failing to migrate.

October 1, 2015

What's new

Click-To-Run editions of Outlook 2013 and Outlook 2016 are now supported.

Windows 10 is now supported.

Migrates email using the Gmail API.

Removed deprecated 2-legged OAuth command line options --google_consumer_key and --google_consumer_secret.

Support Service Account authentication to migrate on behalf of a user from command line using --service_account_json_path option. See Run migration from command line for details.

Optionally collect and report crash data.

What's fixed

Email migration is more resilient to throttling and network or server failures with improved retries with exponential backoff.

Empty email folders on the source are migrated as labels to Gmail.

Messages in Outlook’s Deleted Items now are correctly migrated to Trash.

GAMMO now allows graceful cancellation of a running migration.

Other minor UI issues

April 28, 2015

What's fixed

The migration of secondary calendars was not working correctly. This issue has been fixed.

Removed the deprecated clientlogin command line option --google_password.

Removed the command option --noenable_calendar_fanout as this is the default behavior since moving to the Calendar v3 API.

April 1, 2015

What's fixed

Issue: Client migrations failed if three consecutive 503 backoff responses were received. The client would enter a “throttled” state which quickly exhausted the remaining retry requests and failed the migration with the “Migration failed due to network error” message.

This issue has been fixed. The client now properly performs exponential backoff when receiving 503 requests. The client retries up to 10 times increasing the sleep period exponentially before retrying a request. If a successful event occurs, the retry and sleep times are reset.


March 24, 2015

What's new

Added new command line option --emapi_sleep_time. This setting allows you to increase the number of milliseconds that GSMMO pauses between each email migration API request.

What's fixed

Deleted items were being migrated into the Gmail inbox and not trash. Deleted items now are properly migrated to trash.

Changed the required minimum wait between email migration API requests from 700ms to 1000ms.


December 15, 2014

What's new

GAMMO now uses the latest Email Migration API (version 2).


August 5, 2014

What's fixed

This release fixes the integration with Google Apps Sync for Microsoft Outlook. There was an issue that prevented existing Outlook profiles/PSTs from being imported when creating a new G Suite Sync profile.


July 21, 2014

What's new

GAMMO calendar migrations now uses the latest Google Calendar API (version 3).

Calendar migrations now recognize more time zones.

GAMMO can now get the sender's email address from the message's internet headers even if it's missing from the sender field in Outlook.

What's fixed

This release fixes the following issues:

  • Removed ClientLogin API support, as the API is deprecated. This means that users can now only authenticate using the browser with OAuth.
  • Removed the incorrect request to copy the authorization code during the authorization flow. The prompt now only asks the user to switch back to the application after authorizing access.
  • Fixed an issue where re-migrating secondary calendars would fail if the user had deleted the calendar in G Suite.
  • Fixed issue where the -noenable_label_prefixes command line option was not respected when using the GUI.
  • The command line option -noenable_label_prefixes was renamed to -noenable_label_prefix to be consistent with Google Apps Migration for Microsoft Exchange (GAMME).
  • Fixed a crash that would happen if the password dialog was cancelled when performing a PST migration.

May 22, 2013

What's new

GAMMO now supports Outlook 2013 (32-bit and 64-bit), and runs on Windows 8 in addition to previously-supported operating systems.


Release 2.3
September 15, 2011

What's new

GAMMO is now available in 26 new languages!

GAMMO is now available in 26 languages (in addition to English). Its documentation is available in many of these languages, too.

Which languages are supported?
Chinese simplified
Chinese traditional
Portuguese (Brazil)
Portuguese (Portugal)

GAMMO now matches whichever language the user has defined for Microsoft Outlook, if that language is one that we support. If not, it matches the user's Windows default language, if supported. Otherwise it opens in English.

GAMMO documentation is available in these languages, too. To view documentation in your language, visit the following links and choose your language from the pop-up list at the bottom of the page.

Help for users
Help for administrators


April 29, 2011

What's new

GAMMO now supports SSO via 3-legged OAuth

GAMMO now supports using 3-legged OAuth for migrating users' mail, contacts, and calendar data to G Suite. When running the migration utility, users can now sign in to their G Suite account through a single sign-on (SSO) system—using their current service's login credentials, rather than their G Suite credentials.

3-legged OAuth is also more secure since users can explicitly grant access to their account and then revoke it any time.

The new version also supports a new command-line flag to disable calendar fanouts, creating events only for the user whose data is being migrated—without adding the event to calendars of other attendees. This new flag is useful when performing test migrations.

Google, Google Workspace, and related marks and logos are trademarks of Google LLC. All other company and product names are trademarks of the companies with which they are associated.

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