Nowadays, electronic messaging is the most used network application , and the authentication between users is a vital property. The most commonly employed approaches to ensure this property are PKI and S/MIME email encryption protocols, but indeed they are facing multiples security threats, such as the MITM attack and EFAIL attack. The blockchain is an innovative technology that overcomes these threats and allows to decentralize sensitive operations while preserving a high level of security. It eliminates the need for trusted intermediaries. The blockchain is accessible to all network nodes and keeps track of all transactions already made. The goal of our work is to propose a secure messaging solution based on the blockchain technology. In this paper, we explain why blockchain would make communications more secure, and we propose a model design for blockchain-based messaging maintaining the performance and security of data recorded on the blockchain, using a smart contract to verify the identities and their associated public keys, and validate the users certificate. The system is entirely decentralized and allows users to exchange messages securely.