Unencrypted email is mail sent without transport protection, so its contents may be readable while moving between systems. A network operator positioned along the route, such as a hostile or compromised relay, may be able to observe the message in transit. This differs from end-to-end encryption, which keeps message contents protected from intermediaries.
In cyber security, unencrypted email can expose sensitive information, including account details, personal data, or business communications. Attackers may intercept it on public or otherwise monitored networks. Use encrypted connections between mail systems and enable end-to-end encryption for sensitive messages where practical; remember that transport protection does not necessarily protect a message stored on a mail server or recipient device.