The best tool for Gmail to Office 365 migration should ensure seamless, secure, and efficient transfer of emails, contacts, calendars, and other data. Gmail Backup Tool is an excellent choice for migrating Gmail data to Office 365. It allows users to backup Gmail emails and transfer them directly to Office 365, ensuring no data loss. The tool supports migrating emails, attachments, and folder structures without any hassle. It also provides batch migration, filtering options based on date range, and a preview feature before starting the process.