References
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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