It is important that in general Email Systems must be secure and private. For this reason Zimbra was build on the foundation of an open core system with add-on capabilities and features. Zimbra is the only major Email provider that offers a free, open source software (FOSS) version. In other words the code is available for code audits. Which is a requirement of many governments. This is increasingly important for countries mandating access to source code.
Organisation requires privacy has the option of using Zimbra’s multi server deployment. In other words each component can be independent. Therefore data can be stored securely on different location.
Deployment can be on-premise or cloud hosted solution. Hence organisation has completed control of their own communications. Resulting in improved confidentiality.
Sovereignty means the authority of a state to govern itself or another state. Data Sovereignty generally means your data has to reside in the country. For this reason there are data privacy laws and regulations in your country.