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.
NX (UG or Unigraphics) is also one of the major mechanical CAD software which is developed and marketed by Siemens. Being CAD/CAM/CAE software, it is rapidly growing because it has an advantage of easy configuration with Teamcenter (PLM) which is developed by the same company.