Circle Research has unveiled Chainmail, an open-source prototype utilizing blockchain technology to enhance email security and combat phishing. Chainmail operates as a smart contract on the Ethereum Sepolia test network, serving as a public key infrastructure (PKI) that connects email addresses, PGP keys, and blockchain addresses, allowing users to verify the authenticity of emails without incurring network fees. This initiative seeks to leverage blockchain's inherent PKI capabilities, traditionally used for financial transactions, to create a universal infrastructure, despite challenges such as limited support for diverse digital signatures and potential risks of spam directory creation. Chainmail consists of a smart contract and a Flask-based web application, allowing developers to sign and verify PGP messages, while raising questions about future applications of blockchain as a PKI, including its potential use in chat systems. This project reflects Circle Research's commitment to advancing crypto, blockchain, and Web3 technologies through open-source contributions, offering a platform for experimentation and feedback from the developer community.