The entire concept of electronic mail is based on an analogy: the comparison of sending electronic messages to the sending of paper messages. The analogy works well because e-mail was indeed intended to be like regular mail, only with the advantages of the electronic era: speed and flexibility.

One of the many similarities between electronic and regular mail is the need for addressing. In order for a message to be delivered, it is necessary that the sender specify who the recipient is, and provide a reasonable amount of information to indicate how the recipient can be reached. In TCP/IP electronic mail, a standard electronic mail address format is used for this, and support is also provided for alternative addressing schemes that may be used in special cases.

In this section I describe how electronic mail messages are addressed. I begin with a discussion of standard electronic mail addressing in TCP/IP, and how those addresses are used to determine where e-mail should be sent. I then provide a brief discussion of historical and special e-mail addresses that you may encounter from time to time. I also discuss the use of e-mail address books (aliases) and how multiple recipients may be addressed, as well as providing an overview of electronic mailing lists, one of the earliest ways in which electronic group communication was implemented.