ShareGate Migrate relies on available Microsoft 365 APIs to migrate your mailboxes, and there are a few limitations to consider.
Index
Organizations with Microsoft national cloud limitation
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
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.
Archive mailboxes are not supported.
Encrypted emails are not supported.
Guest mailboxes are not copied.
External users' mailboxes are not supported.
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.
Calendars
Only the default user and shared calendars are supported.
When copying calendars that are shared, Outlook will send sharing notifications to members.
Recurring events without future occurrences, because they were deleted, will not be migrated.
One-time calendar events that have already occurred will not be migrated.
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.
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
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 is a delay for Microsoft 365 to update 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 the other mailbox settings not mentioned in this section are currently not preserved with Copy mailboxes.
Note: There can be a delay before the migrated settings are updated in Microsoft 365 and Outlook.
Supported services
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.