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

This section provides an email message example with 'Content-Transfer-Encoding: 8bit' header to indicate that the content contains 8-bit bytes, commonly used for UTF-8 encoded Unicode characters.

What Is "Content-Transfer-Encoding: 8bit" Email Header? "Content-Transfer-Encoding: 8bit" specifies that the email message content contains 8-bit bytes (all 8 bites are used in each byte).

If "Content-Transfer-Encoding" header is not provided, the default of "Content-Transfer-Encoding: 7bit" is assumed. In this case, the message content should contain 7-bit bytes (the most significant bit is set to 0).

The default of "Content-Transfer-Encoding: 7bit" is good enough, if you just want to send email messages in ASCII characters.

If you want to send UTF-8 encoded Unicode characters, you need to add the "Content-Transfer-Encoding: 8bit" header. Here is a simple example:

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: 8bit

你好! - Hello!

Note that "Content-Type: text/plain; charset=utf-8" header is added to specify that the content contains UTF-8 encoded Unicode characters.

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