DNS: Domain Name Server. This term is used to describe a computer that can be asked to translate a domain name (e.g. mail.mycompany.com) into an IP address usable for transmitting the email message (e.g. 195.62.28.1). Most also support Reverse Domain Name lookups, in which an IP address is translated into a domain name. Usually if a DNS can't translate the name, it will in turn ask other DNS computers it knows about.