The rezpage integration environment including APIs and middleware is designed to keep rezpage inter-operable with a wide range of integrations and interfaces and are built-to-order with required module connections including (but not limited to) corporate web-sites, ERP or finance systems, electronic door access, Single-Sign-On (SSO), POS systems (including xnPOS), CRM systems, Parcel and Locker systems, e-Signing, Utility Meters and residential Internet listing sites.