What is a Email Message ? known as Internet Message or RFC822

About

An email is a document that is composed of the following structure

  • one or more headers
  • followed at the end by a body that may be composed of multiparts

It's a network message known as:

The format is describe in RFC822 Internet Message Format.

The email can be found after the DATA smtp command. ie this is the message.

Structure

An email has:

  • headers (key pair value) such as:
    • the sender’s address,
    • then the recipient’s address
    • address,
    • mimetype, …
  • body (text written in the defined mime format)

where:

  • Every logical line starts without space.
  • A line with a space at the beginning is the continuation of a logical line
  • Headers are separated from the body by a blank line

Example

Delivered-To: [email protected]
Received: by 2002:a05:6504:519b:0:0:0:0 with SMTP id z27csp820130ltq;
        Fri, 12 Jun 2020 12:08:19 -0700 (PDT)
X-Google-Smtp-Source: ABdhPJzM66OAweomG9vKiJ5AWPP0ohl2MoXV5gWEkK6qjMEbbi7zYkA0YtlEAlN2q+zIayLrmH2K
X-Received: by 2002:a7b:c186:: with SMTP id y6mr410599wmi.82.1591988898906;
        Fri, 12 Jun 2020 12:08:18 -0700 (PDT)
ARC-Seal: i=1; a=rsa-sha256; t=1591988898; cv=none;
        d=google.com; s=arc-20160816;
        b=TCI6uKqvNsf837MdYuidYRQJXym4/du4gMiXIDqrfvkJodVd7CFPK3cOoawD8OiT8E
         Hm2dTBOVIOpZElxKAlfFkiUorasnIgTgfSV4GmdmRyRPnb+9kieuIVntFHVYfn1gmQU9
         eXf/M7q/tUl4EH6qyjr3gAgQ1+xAWWhexsGWdAreFfUzNgoVtGDvpbN+VVlQZdt50QWc
         8vdzg04mBmpH3AoB2todjh8TpiDKCJJDVeC6v/bXNZ02T4lL9KRPhr4ZjPQQ/ocS07Ez
         AUGZqgKMSXWswq8Lj7avngjwl5a1yoEb+07pGzJL/lOT9BeWSECwfnC1vexkGVXB/pyR
         XZVw==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=from:message-id:content-transfer-encoding:mime-version:user-agent
         :subject:to:date:dkim-signature:dkim-filter;
        bh=WBggpZrfs7F0OzQkyE7LiZPHyfFFhl7N4CNav2f5YVw=;
        b=0B+TDvc+p0JWW/204sbMHyWdqPQDdEW+3lmKdn2aZu9vuS8Tc1tQmnd3eoEMhRFi0Z
         Vn3LIIBIYnX1oaYlkOWmPuQ5sczzPUxVQbfip0MQ0GDakNwOQJKy+jBMeV3bc+T/KRN3
         yJjFrvfJWwLBoQVIC+lkJVhY3Uj92SM2W7aTL3U3N4P5vvcwIzl1OLEm+aB5kNPbmIj9
         u0Im/2y60y8IOXx2Kh3lrDdJeyFAmrsng5XZDQjL6rM80VA1zm0kA/GUOPgcJE72A5N4
         oBivn/1DdD7piqw3EP6X4u/09owyOvHZW1ENU1GoAFVqPRMvw1s6WF4+eng0j+BensZu
         VeyQ==
ARC-Authentication-Results: i=1; mx.google.com;
       dkim=pass [email protected] header.s=vps748761.ovh.net header.b=ByN4Iw4U;
       spf=pass (google.com: domain of [email protected] designates 164.132.99.202 as permitted sender) [email protected]
Return-Path: <[email protected]>
Received: from server01.bytle.net (server01.bytle.net. [164.132.99.202])
        by mx.google.com with ESMTP id v21si7421752wra.299.2020.06.12.12.08.18
        for <[email protected]>;
        Fri, 12 Jun 2020 12:08:18 -0700 (PDT)
Received-SPF: pass (google.com: domain of [email protected] designates 164.132.99.202 as permitted sender) client-ip=164.132.99.202;
Received: by server01.bytle.net (Postfix, from userid 0)
	id 3E16E1FBE8; Fri, 12 Jun 2020 21:08:18 +0200 (CEST)
DKIM-Filter: OpenDKIM Filter v2.11.0 server01.bytle.net 3E16E1FBE8
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytle.net;
	s=vps748761.ovh.net; t=1591988898;
	bh=WBggpZrfs7F0OzQkyE7LiZPHyfFFhl7N4CNav2f5YVw=;
	h=Date:To:Subject:From:From;
	b=ByN4Iw4U9RP8bzaPK0n3HJbFlvI60ett+V9pkoli+UNtdAcSdq/ANc3hL71PzjrT4
	 3yyTjK3MC5e2f/k+BAnIaAgnradAK/1CbMF4vMZVD6WoVIx7KTZlfWsW39Ir8PhqYQ
	 4TKvPpDUx8ToxUz1gwQlxJoExYW3McXJ2WdvUAf8=
Date: Fri, 12 Jun 2020 21:08:18 +0200
To: [email protected]
Subject: Without hosts dkim test !
User-Agent: Heirloom mailx 12.5 7/5/10
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-Id: <[email protected]>
From: [email protected] (root)
cc: [email protected]
bcc: [email protected]

This is the body of the email

where:

Storage

The mime message are stored in a mailbox

How to see the original email by provider

Gmail

To see the text format of the email (the original), you can ask it in the email menu

Library

Specification

  • 2822 - Internet Message Format
  • 733 - STANDARD FOR THE FORMAT OF ARPA NETWORK TEXT MESSAGES

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