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IETF Request For Comments (RFCs)

The Internet Engineering Task Force (IETF) codifies the decisions it comes to in documents called "Requests For Comments". These are almost universally called by their acronym "RFCs". Many RFCs are the standards on which the Internet is formed. IMC has prepared a brief introduction to Internet standards that gives a bit more background to RFCs.

The level of standardization that an RFC reaches is determined not only by "how good" the RFC is, but by how widely it is implemented and tested. Some RFCs are not solid standards, but they nonetheless document technologies that are of great value to the Internet and thus should be used as guidelines for implementing Internet mail programs.

General References for RFCs

Not all Internet RFCs are standards. Internet standards are subject to extensive review and testing. In the tables below those that are on the standards track are noted by:

• S for Standard (fully adopted)
• D for Draft (initial testing)
• P for Proposed (entry level)
• H for Historic

A good discussion of the difference between standards and RFCs is Not All RFCs are Standards (RFC 1796).

For more information on how standards are made in the IETF, please see the article Making Standards the IETF Way by Dave Crocker, one of the founders of the IMC. The official rules for how RFCs are made and how things become standards are stated in RFC 2026.

Before a proposal or note becomes an RFC, it is set down as an Internet Draft (I-D) and discussed in various forums, often working groups of the IETF. Because I-Ds are often rough drafts and subject to major changes, they are described in a different document. The IMC has created a separate list of I-Ds relating to Internet Mail.

Types of Internet Mail Standards and Protocols

Internet mail standards and protocols fall into some broad categories. Of course, some standards straddle more than one category, but they can all fit into at least one of the following:

• Host-to-host mail transfer (SMTP)
• Client-to-host communication (POP, IMAP)
• Basic message format and encoding (RFC822)
• Multipurpose Internet Mail Extensions (MIME)
• Message and transmission security
• Internationalization
• Gateways to non-Internet mail (mostly X.400)
• Calendaring and Scheduling
• Miscellaneous

Many of the terms in the Internet mail world can be confusing. There is an excellent basic explanation of what terms are used for Internet mail transports, clients, servers, and so on in Classifications in E-mail Routing (RFC 1711).

Host-To-Host Mail Transfer

Client-To-Host Communication

Basic Message Format and Encoding

Multipurpose Internet Mail Extensions (MIME)

Message and Transmission Security

Internationalization

Gateways to Non-Internet Mail

Calendaring and Scheduling

Miscellaneous