A mail server is a computer that stores e-mail account settings and manages incoming and outgoing e-mail messages between other mail servers. For example, when you send e-mail from your computer, it first goes to a mail server, and then the mail server routes it to your recipient. When your recipient accesses their e-mail account, your message is downloaded from their mail server and appears in their inbox. Also known as an e-mail server or a virtual post office.