Список RFC
RFC821 - SIMPLE MAIL TRANSFER PROTOCOL
RFC2821 - Simple Mail Transfer Protocol (Obsoletes 821, 974, 1869)
RFC5321 - Simple Mail Transfer Protocol (Obsoletes 2821)
RFC822 - STANDARD FOR THE FORMAT OF ARPA INTERNET TEXT MESSAGES
RFC2822 - Internet Messages Format (Obsoletes 822)
RFC5322 - Internet Messages Format (Obsoletes 2822)
RFC1912 - Common DNS Operational and Configuration Errors