There are over 2500 RFC's. Each RFC is known by a number. For instance, RFC 1180 presents a tutorial on TCP/IP, RFC 1920 lists the current standards RFC's and explains the RFC standards process, and RFC 1941 is a FAQ list on the topic of Internet deployment in educational establishments.
MX record. A mail exchanger record (MX record) is a type of resource record in the Domain Name System that specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value used to prioritize mail delivery if multiple mail servers are available.
n MX record, or Mail Exchanger record, is a DNS record pointing to the server that is responsible for handling email for a given domain. You can send emails without the MX record configured for your domain name, but you will not be able to receive emails without it. It is important that you have working Name Servers so that they can answer queries about necessary domain name records: The following syntax is commonly used by many DNS hosting providers: 1  Host: your domain name. 2  Priority/Preference: number. 3  Destination/Mail Server/Points to: your mailing server name.