Zimbra does not officially support Centos, why?

Zimbra at this point in time do not officially support Centos. However, Agileware and many others in the Zimbra community have large production Zimbra deployments on Centos which are operating perfectly. As explained on the Centos website: “CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible”. There is a Request for Enhancement with Zimbra to official support Centos, see this Official Support for ZCS Network Edition on CentOS RFE #23487. For more details on this topic, see Zimbra CentOS support posts.