Watchpoints and best practices for Exchange

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


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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 Accelerate Old Messages in the settings template, you are likely to see 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. Learn more

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, G Suite 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–Microsoft 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, G Suite Migrate re-creates these folders using labels in Gmail. The sync issues in these messages do not relate to the G Suite 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. For details, see Understand Exchange settings templates.

Deleted items–Email messages that are in the Deleted Items folder in Exchange for 30 days or more will not be migrated. These messages 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. In the email, a link to the attachment is added to the end of the email. You can configure the size threshold and Drive folder name for these attachments in the settings template. Learn more about 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. For details, go to Monitor progress with logs.

For troubleshooting information, see Missing email messages

Migrating to Google Groups—When viewed in Google 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 Google Groups.
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 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. See Requesting higher quota.

Calendar resources–Identity mapping Make sure that you map calendar resources in an identity mapping. For details, see Create and 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 (see Calendar resources–super administrator accounts).

You can use content compliance rules to deliver these messages to email quarantines. For details, see Set up rules for content compliance.

Calendar resources–Super administrator accounts

By default, G Suite 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. For details, see 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 G Suite 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 G Suite 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–The 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 GUser's primary calendar. Check your mapping carefully before proceeding.

Other types of data
Watchpoint Best practices
Exchange contact notes Unlike G Suite, there is no limit to the notes size for an Exchange contact.

When contact notes are migrated, large notes might be truncated in G Suite. 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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