Email Tutorials - Herong's Tutorial Examples - v1.04, by Herong Yang
Subject: =?...?= - 7-Bit Encoding
This section provides an email message example with 'Subject: =?...?=' header to specify character set and byte encodings to protect non-ASCII characters in the email subject.
What Is "Subject: =?...?=" Email Header? "Subject: =?...?=" specifies that the email message subject is 7-bit encoded to protect non-ASCII characters. The encoded text uses the following format:
=?charset_encoding?byte_encoding?encoded-text?=
where:
charset_encoding = the character set encoding name, e.g. utf-8.
byte_encoding = the byte encoding ID, e.g. B (Base64)
or Q (Quoted-Printable).
examples:
Subject: =?utf-8?Q?=E4=BD=A0=E5=A5=BD=EF=BC=81_-_Hello!?=
Subject: =?utf-8?Q?=E4=BD=A0=E5=A5=BD=EF=BC=81?= - Hello!
Subject: =?UTF-8?B?5L2g5aW977yBIC0gSGVsbG8h?=
For more information, see "RFC1342 - Representation of Non-ASCII Text in Internet Message Headers" at datatracker.ietf.org/doc/html/rfc1342
Here is a simple example of email message with a Quoted-Printable encoded text in the subject.
Return-Path: <joe@herongyang.com> Delivered-To: herong@herongyang.com Received: from 127.0.0.1 (localhost [127.0.0.1]) by mail.herongyang.com (Postfix) with ESMTP id 5EABD266002B for <joe>; 15 Nov 2023 06:19:34 -0500 (EST) Message-Id: <20231113111946.5EABD266002B@mail.herongyang.com> Date: 15 Nov 2023 06:19:34 -0500 (EST) From: joe@herongyang.com Subject: =?utf-8?Q?=E4=BD=A0=E5=A5=BD=EF=BC=81?= - Hello! Can you read the Chinese characters in the "Subject" header?
Table of Contents
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