Replace current website with Homestead site while keeping accessible via old URLs

Our organizations current website is accessible via 2 domains, each registered by different registrars (Register.com and ENOM.com). We have now created a new website with Homestead that we want to replace our current site and we would like it accessible via the 2 older domains. We host our own email on an inhouse Exchange server that is also accessible via the 2 older domain names. How should we proceed to have the Homestead website replace the older site yet remain accessible via the older domain names (all without disrupting our email)? Thanks for your assistance.