If your on-premises users are using personal email retention tags in custom folders in an archive mailbox, the tags are removed ...

If your on-premises users are using personal email retention tags in custom folders in an archive mailbox, the tags are removed and changed to "Use parent folder policy" when an on-premises mailbox and archive is moved to %BRAND_EXCHANGE_ONLINE_SHORT% Online. You will need to export the on-premises retention tags from the on-premises organization and import the retention tags in your %BRAND_OFFICE_365_SHORT% organization. To learn more, see Export and import retention tags.