Several different operating systems are used by KD Interactive Hosted Email to provide email services, administrative services, and supporting services. All operating systems in use are security hardened by KD Interactive Hosted Email and receive security and performance updates soon after release from the operating system vendor.

Founded in 1993, Red Hat is the most recognized Linux brand in the world, serving global enterprises through technology and services made possible by the open source model. Red Hat's Enterprise Linux family of operating systems provides extreme stability, performance, and scalability for mission-critical systems. The operating systems have a 12-18 month release cycle and are backed by seven years of technical support for every version. Red Hat Linux is the platform for all core email services at KD Interactive Hosted Email.

CentOS is a free, open-source clone of Red Hat Enterprise Linux. CentOS conforms fully with Red Hat's redistribution policy and aims to be 100% binary compatible. Many of the KD Interactive Hosted Email servers, especially development servers, run CentOS.

Microsoft Corporation made big strides in stability and performance over previous revisions of its Windows Server product when it released the 2003 version. Windows Server hosts many KD Interactive Hosted Email administrative tools, including most of the administrative SOAP API.