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Copy mailboxes - Limitations

Updated over 3 weeks ago

ShareGate Migrate relies on the Microsoft 365 APIs to migrate your mailboxes, and several limitations should be considered.

Organizations with Microsoft national cloud limitations

Due to several restrictions with these environments, the following Microsoft national cloud deployments are not currently supported for Copy mailboxes:

  • Microsoft 365 US Government - GCC

  • Microsoft 365 US Government - GCC High and DoD

  • Microsoft 365 China, operated by 21Vianet

Supported services

Only migrations of mailboxes from Exchange Online and Google Workspaces to Exchange Online are supported in ShareGate Migrate.

Other services, such as Slack, are not currently supported.

For Google Workspaces migrations, see Copy from Gmail overview.

Copy Limitations

Bandwidth limitations

  • The maximum migration speed of a single mailbox is 1.5 gigabytes of data per hour.

  • We do not recommend single Mailbox copy actions that exceed 800,000 items, as they become difficult to troubleshoot.

Tip: Copy one mailbox first to get a feel for how many mailboxes you can copy simultaneously. For more tips, see Copy mailboxes - Best practices.

Emails

  • The only supported mailbox types are User and Shared mailboxes.

  • Room and equipment mailboxes are not supported.

  • Encrypted emails are not supported.

    • Because ShareGate Migrate cannot detect encrypted emails, they are migrated normally and cannot be read at the destination.

  • Folder permissions are not preserved.

  • Shared, public, and archived folders are not supported.

  • Email retention policies are not preserved.

  • Loop components are not supported.

  • Disconnected or disabled mailboxes are not copied.

  • Mailboxes of users deactivated in Active Directory (AD) are not copied.

  • Attached emails or events are not supported.

  • Reference attachments, such as a link to a document on OneDrive for Business, are not supported.

  • Message headers are not preserved.

  • Scheduled emails are not preserved with their schedules and are copied as draft emails.

  • Messages from an RSS feed are not supported.

  • Outlook notes (OneNote links in the Notes folder) are not supported.

Calendars

  • Only default user, group, and shared calendars are supported.

  • When copying calendars that are shared, Outlook will send sharing notifications to members.

  • When copying meetings, Outlook will send sharing notifications to members.

  • Recurring events without future occurrences, because they were deleted, will not be migrated.

  • The mailbox of the organizer of an event must be part of the migration for events to get copied.

    • If the organizer is external, the event gets forwarded.

  • The Teams meeting link is not preserved in the body of recurring events.

    • The button to join the meeting in the Teams client and the link in the master event are still available at the destination.

  • Email reminders are not supported.

  • If no past events are copied, exception-type events with future occurrences can only be copied from the copy date up to 1825 days (or roughly 5 years).

    • If past events are included and you specify a start date, exception-type events with past and future occurrences can only be copied 1825 days (or roughly 5 years) after the specified start date.

    • If past events are included and no start date is specified, exception-type events with past and future occurrences can only be copied 912 days (or roughly 2.5 years) before or after the copy date.

    • Attendees will only appear in the event descriptions and won't receive a notification for the migrated past events.

    • Only the organizers will see the copied events at the destination.

Contacts

  • Contact lists are not migrated.

  • Contact category colors are not copied.

    • Every contact category becomes red at the destination.

    • The category color is only visible with the new Outlook at the destination.

  • Favorite statuses for your contacts are not preserved (The star icon next to your contacts).

  • The following phone properties are not copied:

    • Organization Main Phone

    • Radio phone

    • Assistant Phone

    • Callback Phone

    • Telex

    • TTY

    • Parent folder ID

Group mailboxes

  • Content in the Files tab is not copied

    • The files are stored in a SharePoint site, and you can use Copy content only to migrate them.

  • The members of the group are not copied; only the content of the group mailbox.

  • Emails that are manually moved after a migration get duplicated during an incremental copy.

  • Rules are not supported.

  • Group mailboxes of groups without owners are not copied.

Archive mailboxes

  • It can take some time before the archive is visible and usable in Outlook after enabling it.

  • The sender of a draft email in the archive is not preserved.

  • Emails that are manually moved after a migration get duplicated during an incremental copy.

Categories

  • Favorite statuses for your categories are not preserved (The star icon next to your categories).

To Do app

  • The To Do app and its tasks are not supported.

Mailbox rules

  • Mail flow rules (transport rules) are not supported.

  • These rule options are not supported:

    • Before (condition/exception).

    • After (condition/exception).

    • Pin to top (action).

Graph Extensions

  • Custom properties added through Graph extensions are not supported.

Mailbox settings limitations

Only limited support is currently offered for your mailbox settings described below:

Time zone

The mailbox Time zone is preserved and synced across myaccount.microsoft.com, Outlook general settings, and Outlook calendar settings.

Most Time zone options are not preserved, including:

  • The option: When I travel across time zones, ask me if I want to update my time zone.

  • The label under Display my calendar in time zone.

  • The Other time zones options.

Note: There may be a delay in Microsoft 365 updating your time zone at the destination. If your time zones do not match, wait around 15 minutes after the migration, and it will get updated automatically at the destination.

Automatic reply

Some Automatic reply settings are preserved, including:

  • The option Send replies only during a time period.

  • The option Send automatic replies inside your organization (with formatting)

  • The option Send replies outside your organization and send replies only to contacts (including the message with formatting).

Other Automatic reply settings are not supported, including:

  • The option Block my calendar for this period.

  • The option Automatically decline new invitations for events that occur during this period.

  • The option Decline and cancel my meetings during this period.

Other settings

All other mailbox settings not mentioned in this section are not preserved when copying mailboxes.

Note: There can be a delay before the migrated settings are updated in Microsoft 365 and Outlook.

Source and destination support

You can only copy mailboxes from a Microsoft 365 source tenant to a different Microsoft 365 destination tenant.

Missing users

If you notice missing users, verify the following:

  • Users have valid Microsoft licenses.

  • Users are not blocked in Microsoft Entra ID.

  • Users have the MEMBER user type.

Connection limitation

Connections with Copy mailboxes are not synced with the ShareGate Explorer in ShareGate Migrate.

You must make a separate tenant connection when using that feature. You can add a new connection for the source and the destination, and you can only disconnect a tenant during the source connection process.

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