Postfix is a Mail Transport Agent (MTA). This software provides the SMTP services for ClearOS.
In order to support Kolab, Postfix version 2.4.0 or later is required (or a patched version of earlier versions). ClearOS 5.x uses a more recent version of Postfix to meet these requirements.
It will no longer be necessary to maintain this software package with the release of ClearOS 6.0.