Applies to: Customers migrating to G Suite from another email system using one of the G Suite migration tools (example: G Suite Migration for Microsoft Exchange).
Before migrating, folders nested under the Inbox should be moved. If they are not moved the migration tool will prefix labels with an underscore to ensure proper nesting in the Gmail web interface. For example, a folder named "Inbox/Receipts" is migrated as "_Inbox/Receipts.
Email clients setup with IMAP translates folders with forward slashes (/) into separate folders. See:: https://support.google.com/mail/answer/77657?hl=en. The forward slash should be replaced or the folders re-organized before migrating.
Messages larger than 25GB will not be migrated. See Gmail’s attachment limit: https://support.google.com/mail/answer/6584?hl=en. Large attachments could be stored in Google Drive, archived, etc.