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 Mailtrust.  

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 Mailtrust 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 Mailtrust administrative tools, including most of the administrative SOAP API.