Content-Type: text/html - HTML Content

This section provides an email message example with 'Content-Type: text/html' header for HTML formatted message content.

What Is "Content-Type: text/html" Email Header? "Content-Type: text/html" specifies that the email message content is an HTML formatted document. It tells the email client tool to render the content into a formatted Web page.

"text/html" and other "Content-Type" values are defined in "RFC1341 - MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies" at

If "Content-Type" header is not provided, the default of "Content-Type: text/plain" is assumed. In this case, the message content contains text without any formatting.

The default of "Content-Type: text/plain" is good enough, if you just want to send a short greeting message to your friend.

If you want to send nice looking wedding invitation, you can create the invitation as an HTML document and send it with the "Content-Type: text/html" header. Here is a simple example:

Return-Path: <>
Received: from (localhost [])
  by (Postfix) with ESMTP id 5EABD266002B
  for <herong>; 15 Nov 2023 06:19:34 -0500 (EST)
Message-Id: <>
Date: 15 Nov 2023 06:19:34 -0500 (EST)
Content-Type: text/html

<p style="text-align: center">
<span style="font-family: 'Dancing Script'; font-size: 4em">Chloe
<span style="font-size: 0.5em">&</span> Oliver</span><br/>
<span style="font-family: sans-serif; font-size: 1em">
<span style="font-size: 2em">JULY 7, 2027</span></span>

When an email client tool receives a message with "Content-Type: text/html", it will render the message content like a Web page based on embedded HTML tags. Text paragraphs can be styled. References can become clickable links. Data elements can be organized into tables. Images and videos can be embedded directly.

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