MeSince is an encrypted communication system based on email system which takes our PKI technical advantages. MeSince is the world's first default automatic S/MIME encryption email client that enables all messages been encrypted, digitally signed and timestamped by default automatically for free. MeSince has solved the S/MIME’s inefficient and poor user experience problem to let email encryption non-inductive and automatic. MeSince supports Cryptographic Key Management System to let enterprise manage the encryption private key by itself. MeSince®, lets every email be encrypted automatically to eliminate email leak. MeSince®, lets every email has an identity automatically to eliminate email fraud.