RFC is Request For Comments

• RFC 2821 Simple Mail Transfer Protocol (SMTP)
• RFC 2822 Internet message format
• RFC 1123 Requirements for Internet hosts
  (updates and clarifications to various earlier RFCs, some of which are included in the more recent mail RFCs above)
• RFC 2119 Key words for use in RFCs (use of keywords SHOULD, MUST etc)
• Building Internet Firewalls (2nd edition), Elizabeth D Zwicky, Simon Cooper, D Brent Chapman; O'Reilly & Associates Inc, ISBN 1-56592-871-7