E-mail addresses have a fixed format: user@mail.server.name, where user is the recipient's account and mail.server.name is the recipient's e-mail server name. It can also be a domain name or IP address expressed in decimal numbers.

In the network, the e-mail box can automatically receive the e-mail sent by any e-mail box on the network, and can store electronic files with specified size and other formats. E-mail has a separate domain name, and its e-mail address is marked after @. The general format of e-mail is: user name @ domain name.

E-mail service is an information transmission service based on computer and communication network, which provides users with various types of information such as e-mail, digital fax of documents, images and digital voice by means of electric signal transmission and information storage. E-mail enables people to send and receive letters at any time, which solves the limitation of time and space and greatly improves work efficiency.