Watchpoints & best practices for Exchange

Before you begin to migrate content from Microsoft Exchange, make sure you review the Google Workspace Migrate best practices. Then, familiarize yourself with the following points. 


Watchpoint Best practices
Email forwarding—To avoid duplicates and errors, email messages are checked to make sure they don’t already exist in the target mailbox. If you use email forwarding and enable the Accelerate Old Messages setting, you are likely to get some data duplication.

If you enable Accelerate Old Messages with email forwarding, set Insert Before Date field date to the day before forwarding was turned on. Doing so reduces the risk of data duplication. Go to Migrate Exchange content.

System sublabels—While Exchange supports subfolders under all folders, some Gmail labels (such as Spam or Trash) can't have sublabels. During a migration, a new label is applied to subfolders that don’t have a corresponding label.

For example, if a user has a subfolder under Spam, Google Workspace Migrate creates a new label for that folder. The migrated email will have the Spam and subfolder label applied.

Before you migrate, tell your users about this change.
Sync issues label–Outlook has nested folders under the Sync issues folder. These folders contain logs and items that Outlook can’t synchronize with your Outlook email or SharePoint servers.

During a migration, Google Workspace Migrate re-creates these folders using labels in Gmail. The sync issues in these messages are unrelated to the Google Workspace Migrate migration process.

Before you migrate, tell your users about this issue. If you want to filter out the content, you can create a filter in the Exchange settings template to exclude the Sync issues folder and its children. Go to Understand Exchange settings templates.

Deleted items–Email messages that are in the Deleted Items folder in Exchange for 30 days or more aren't migrated because Trash items in Gmail are permanently deleted after 30 days.

You are unable to change the 30-day deletion policy for Trash messages in Gmail. Advise your users about this issue. Learn more about Gmail storage settings.
Large attachments—All email attachments over 25 MB are added to Google Drive. A link to the attachment is added to the end of the migrated email. You can configure the size threshold and Drive folder name for these attachments in the settings template. Go to Exchange settings templates
Date headers in email—If a source email has an invalid headers for its date, the message appears in the target mailbox as having arrived at migration time.

The issue is caused by email messages with date headers that don't conform to the RFC-2822 standard.

Advise your users about this issue.
Difference in the total amount of email messages—Following a migration, you might notice that the number of email messages in the source environment exceeds the number of messages migrated to Gmail.

This discrepancy might be due to the difference between folders in Exchange and labels in Gmail. In Exchange, when you assign a message to more than one folder, the message is duplicated. Following a migration, the duplications are removed in Gmail and different labels are applied instead. 

To verify that all messages have been migrated, check the logs for any errors. Go to Monitor progress with logs.

For troubleshooting information, go to Missing email messages

Migrating to Google Groups—When viewed in Groups, migrated email messages appear as read by the user who sent them. For other group members, the messages appear as unread.  Advise your users that the read and unread state from the source mailbox is not retained in Groups.
Links in email messages might be crawled by Gmail during a migration.

Gmail scans migrated email messages for security and threat issues. In some cases, Gmail crawls links included in the body of email messages.

You can avoid this issue by using the Accelerate old messages option in your settings template. Before you use the setting, make sure you’re fully aware of how it works. For details, go to Understand Exchange settings templates.

Exchange email filters—The following actions and conditions don’t have an equivalent in Gmail:


  • Forward as attachment to recipient
  • Permanent delete
  • Send SMS alert to recipient
  • Server reply with message
  • Stop processing rules


  • Category
  • Flagged for action
  • From connected account
  • Importance
  • Is approval request
  • Is automatic forward
  • Is automatic reply
  • Is encrypted
  • Is meeting request
  • Is meeting response
  • Is non-delivery report
  • Is permission controlled
  • Is read receipt
  • Is signed
  • Is voicemail
  • Item class
  • Message classification
  • Not sent to me
  • Sensitivity
  • Sent cc me
  • Sent only to me
  • Sent to me
  • Sent to or cc me
  • Within date range
Exchange filters with these actions or conditions are ignored during the migration. Advise your users about this issue.


Watchpoint Best practices
Calendar migrations–API limits If you are running a large migration (1,000+ calendars), you might reach the Google Calendar API daily limit and see 403 errors. You can request an increase to the daily limit for the Calendar API.

Run a scan to get the total number of events you need to migrate. Then, determine how many events you're likely to migrate in a 24-hour period and request a Calendar API quota of 3 times that amount. Go to Requesting higher quota.

Calendar resources—Steps to migrate

Resources must be created manually or by bulk import in the target domain. For details, go to Set up buildings, features & Calendar resources.

To migrate their calendars and event associations: 

  1. Add your source and target calendar resources to the mapping. Use the following headers: 
    • Source ExchangeUser–Use the email address of the Exchange calendar resource. 
    • Target GCalendarResource–Use the email address of the Google Calendar resource. 

    For details, go to Create & manage a mapping.

  2. Map the calendar resources in an identity mapping. Go to Create & manage an identity mapping.
Calendar resources–Auto-accept meetings

If the calendar resource is set to Auto-accept meetings that don't conflict (the default), and conflicting bookings are migrated, the meeting organizer receives an email for each declined invitation. The super administrator also receives an email. Go to Calendar resources–super administrator accounts.

You can use content compliance rules to deliver these messages to email quarantines. Go to Set up rules for content compliance.

Calendar resources–Super administrator accounts

By default, Google Workspace Migrate uses all super administrator accounts to write calendar resource events to the target domain. Using super admin accounts increases migration speed and reduces the risk of quota issues.

Before you begin:

Following a migration:

  • If the calendar resource is set to Auto-accept meetings that don't conflict, the default and conflicting bookings are migrated, the super admin (and the organizer) receives an email notification for all declined invitations. You can use content compliance rules to deliver these messages to email quarantines. Go to Set up rules for content compliance.
  • In the resource's calendar, the event shows as “Created by” the super admin. The activity is tracked in the Calendar audit log.

You can turn off this behavior with the Use all super admins to write resource calendar events setting in the Exchange settings template. When the setting is turned off, only the Google Workspace Migrate admin account is used to migrate calendar resources. 

Calendar resources–Created after January 21, 2020 If you attempt to migrate to Google calendar resources that were created after January 21, 2020, you might see unexpected Location Not Found errors.

To resolve these errors, upgrade to Google Workspace Migrate version For details, see Upgrade the software

Primary to secondary calendar migration

To map a primary calendar to a secondary calendar on your target domain, use a GCalendar entry in your mapping.

Your mapping should include:

  • Source ExchangeUser–Email address of the owner of the primary calendar.
  • Source ExchangeCalendar–The path to the primary calendar (usually /Calendar).
  • Target GUser–Email address of the owner the secondary calendar.
  • Target GCalendar–Google Calendar's calendar ID (for example, The Google Calendar must be created prior to the migration. You can use the Google Calendar API to create calendars.
  • MapChildrenOnly–True. This is required to map calendar events to a pre-existing calendar.

Important: If the mapping is misconfigured, events might be migrated to the target user's primary calendar. Check your mapping carefully before proceeding.

Other types of data

Watchpoint Best practices
Exchange contact notes Unlike Google Workspace, there is no limit to the notes size for an Exchange contact.

When contact notes are migrated, large notes might be truncated in Google Workspace. Advise your users about this issue.

Next step

Now it's time to set up an Exchange connection. To get started, see Add an Exchange connection.

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