Functions

Additional standard clauses may be added in this location by future standards and registration with IANA. SMTP servers SHOULD NOT use unregistered names. See Section 8.

Additional standard names for links are registered with the Internet Assigned Numbers Authority (IANA). “Via” is primarily of value with non-Internet transports. SMTP servers SHOULD NOT use unregistered names.

Additional standard names for protocols are registered with the Internet Assigned Numbers Authority (IANA) in the “mail parameters” registry [9]. SMTP servers SHOULD NOT use unregistered names.

By-domain = CFWS “BY” FWS Extended-Domain

Extended-Domain = Domain / ( Domain FWS “(” TCP-info “)” ) / ( address-literal FWS “(” TCP-info “)” )

For = CFWS “FOR” FWS ( Path / Mailbox )

From-domain = “FROM” FWS Extended-Domain

ID = CFWS “ID” FWS ( Atom / msg-id ) ; msg-id is defined in RFC 5322 [4]

Link = “TCP” / Addtl-Link

Opt-info = Via With ID For [Additional-Registered-Clauses]

Protocol = “ESMTP” / “SMTP” / Attdl-Protocol

Return-path-line = “Return-Path:” FWS Reverse-path

Stamp = From-domain By-domain Opt-info CFWS “;” FWS date-time

Information derived by server from TCP connection not client EHLO.

Time-stamp-line = “Received:” FWS Stamp

Via = CFWS “VIA” FWS Link

With = CFWS “WITH” FWS Protocol