Which of the following terms refers to a digital or electronic message that is sent over the internet?

The term that specifically refers to a digital or electronic message sent over the internet is email. Email, short for electronic mail, is a method of exchanging digital messages between people using electronic devices. It involves sending data packets through various protocols and connects users across the globe instantaneously. The convenience and speed of email make it a primary mode of communication in both personal and professional settings.

In contrast, a letter typically refers to a written message delivered through postal services and not electronically. The term message is broader and can encompass various forms of communication, including spoken or written interactions, not limited to electronic formats. Notification may refer to alerts or updates that can come from various applications or services, but it does not specifically denote a message sent over the internet like email does. Thus, email is the most accurate term for a digital message sent electronically.