Despite email's importance as a communication method, security and privacy were not built into the The Simple Mail Transfer Protocol (SMTP) protocol ↗. As a result, email is a major attack vector.
Email security is the process of preventing email-based ↗ cyber attacks and unwanted communications. It spans protecting inboxes from takeover, protecting domains from spoofing ↗, stopping phishing attacks ↗, preventing fraud, blocking malware ↗ delivery, and filtering spam ↗.