2369: The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields.

The mailing list command specification header fields are a set of structured fields to be added to email messages sent by email distribution lists. Each field typically contains a URL (usually mailto [RFC2368]) locating the relevant information or performing the command directly. The three core header fields described in this document are List-Help, List-Subscribe, and List-Unsubscribe.