Email Tutorials - Herong's Tutorial Examples

∟Email Message Format and Headers

This chapter provides introductions and tutorial examples on email message format. Topics include email message headers and content; commonly used header names; encoded non-ASCII characters in content and headers; HTML formatted content; attachment files; email message examples.

Email Message Format and Example

What Are Email Message Headers

Content-Type: text/html - HTML Content

Content-Type: multipart/alternative; boundary="..."

Content-Type: multipart/mixed; boundary="..."

Content-Transfer-Encoding: 8bit - Non-ASCII Content

Content-Transfer-Encoding: base64 - Base64 Encoded Content

Content-Transfer-Encoding: quoted-printable - 7-Bit Encoding

Subject: =?...?= - 7-Bit Encoding

From: ... - Email "From" Address

To: ... - Email "To" Addresses

Received: from ... by ... - SMTP Server Log

Takeaways:

• An email message contains a header section and a content section, separated by an empty line.
• A header line contains a header name and its value, separated by (: ).
• Message content type is assumed as "Content-type: text/plain", if not overridden.
• "Content-type: text/html" specifies that the message content is an HTML formatted document.
• "Content-Type: multipart/alternative" specifies that the email message content contains multiple alternative parts.
• "Content-type: multipart/mixed" specifies that the message content contains multiple separate parts: the main content and attached files.
• Message content encoding is assumed as "Content-Transfer-Encoding: 7bit", if not overridden.
• "=?...?=" encapsulates Base64 or Quoted-Printable encodings of non-ASCII characters in headers and content.
• "Received: from ... by ..." header records a log message when the email message was transmitted to a new SMTP server.

Table of Contents

 About This Book

 Introduction to Email

 Postfix - Mail Transport Agent (MTA)

 SSL/TLS Secure Connections with Postfix Server

 Dovecot - IMAP and POP3 Server

 SSL/TLS Secure Connections with Dovecot Server

 Email Client Tools - Mail User Agents (MUA)

 Mozilla Thunderbird - Mail User Agents (MUA)

 PHPMailer - PHP Package for Sending Emails

►Email Message Format and Headers

 References

 Full Version in PDF/EPUB

Email Message Format and Headers - Updated in 2024, by Herong Yang