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

This section provides an email message example with 'Content-Transfer-Encoding: quoted-printable' header to indicate that the content is Quoted-Printable encoded, commonly used for protecting non-ASCII characters.

What Is "Content-Transfer-Encoding: quoted-printable" Email Header? "Content-Transfer-Encoding: quoted-printable" specifies that the email message content is Quoted-Printable encoded. In the encoded output, any 8-bit byte will be converted to the escape character (=) followed by the two hexadecimal digits representing the original byte. The encoded output contains only 7-bit bytes and safe to be transmitted between SMTP servers.

Comparing to Base64 encoding, Quoted-Printable encoding results a fairly readable output, if the original content only contains a small number of 8-bit characters.

Here is a simple example of email message with the same content as the one in the previous tutorial. But it is delivered as a Quoted-Printable encoded content.

Return-Path: <>
Received: from (localhost [])
  by (Postfix) with ESMTP id 5EABD266002B
  for <joe>; 15 Nov 2023 06:19:34 -0500 (EST)
Message-Id: <>
Date: 15 Nov 2023 06:19:34 -0500 (EST)
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

=E4=BD=A0=E5=A5=BD=EF=BC=81 - Hello!

If you are looking for more examples of Quoted-Printable encoded email content, you can find them in emails originated from

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

 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


 Full Version in PDF/EPUB