與郵件系統相關的國際標準協議：
RFC 821 - Simple Mail Transfer Protocol
RFC 822 - Standard For The Format Of ARPA Internet Text Messages
RFC 974 - Mail Routing And The Domain System
RFC 1123 - Requirements for Internet Hosts -- Application and Support
RFC 1652 - SMTP Service Extension for 8bit-MIMEtransport
RFC 1842 - ASCII Printable Characters-Based Chinese Character Encoding
RFC 1869 - SMTP Service Extensions
RFC 1892 - The Multipart/Report Content Type for the Reporting of Mail System
RFC 1893 - Enhanced Mail System Status Codes
RFC 1894 - An Extensible Message Format for Delivery Status Notifications
RFC 1939 - Post Office Protocol - Version 3
RFC 1957 - Some Observations on Implementations of the Post Office Protocol (POP3)
RFC 2197 - SMTP Service Extension for Command Pipelining
Requests For Comments
http://www.freesoft.org/CIE/RFC/index.htm