Email is the second-largest traffic on the Internet and one of the key communication tools for digital transformation, but since email services have all moved to the cloud, email is no longer in your own mail server. To protect the security of emails containing a large amount of personal confidential information and business secrets, the principle of zero trust must be adopted. Zero trust to the emails that stored in cleartext in the cloud. Every email must be encrypted to ensure that each email is stored in ciphertext in the cloud. The upcoming ZoTrus Email Security Cloud Service is a full-lifecycle email security solution that realizes end-to-end encryption, it is an email security solution that integrates email encryption, digital signature, and digital postmark (timestamp), which can effectively eliminate email security issues such as email fraud, email leaks, and email identity spoofing, thereby ensuring the security of digital business communications.