Mail server
Remote or central computer that holds electronic mail (e-mail) messages for clients on a network. When the user requests his or her e-mail they contact the mail server, which delivers to the client computer all mail being stored.
Tip: When trying to find a mail server address, search for the POP3 and SMTP address. For example, with the Gmail mail server address is pop3.gmail.com and smtp.gmail.com. The address used is unique to the mail server you want to use to send and receive e-mail.
In the real world, a mail server is similar to the post office, where mail is stored and sorted before being sent to its final destination.
Also see: E-mail, Mail transfer agent, Network definitions