A party that takes actions detrimental to the sender or receiver of messages, an organization, or the Internet at large. It is a fairly broad term because the number of malicious things that can be done with, to, or through email is rather large and difficult to document. A Spammer might be referred to as a Malicious Actor; somebody who phishes, or sends messages that seek to infect or subvert computers and/or networks would definitely fall under this category.

A party that takes actions detrimental to the sender or receiver of messages, an organization, or the Internet at large. It is a fairly broad term because the number of malicious things that can be done with, to, or through email is rather large and difficult to document. A Spammer might be referred to as a Malicious Actor; somebody who phishes, or sends messages that seek to infect or subvert computers and/or networks would definitely fall under this category.