When migrating data to Office 365 Exclaimer (https://exclaimer.com/email-signature-handbook/mastering-office-365-data-migration-for-seamless-transitions/), key considerations include thorough planning, ensuring data integrity, and minimizing disruption to users. Best practices involve conducting a detailed system audit, setting up data migration tools, and testing before full implementation. A phased approach ensures smoother transitions, while ongoing user communication and support help address any issues quickly. Post-migration validation is crucial to confirm data accuracy and system functionality.