Send Your Email Marketing Messages as Multipart Alternative

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Some users have set their email preferences to accept messages in HTML format, while others may have chosen to receive emails only in plain text to combat privacy and security issues. ​If you're sending a marketing email, sending your messages as multipart alternative will display your message correctly in either HTML or plain text formatting, so you'll be able to reach more of your prospects.

What Is Multipart/Alternative?

Multipart/alternative emails contain both plain text and HTML. What a user sees depends on their set preferences or what's allowed by their email client. If an email client can't render HTML messages, it will display the plain text version. HTML-enabled email programs will usually show the rich HTML version unless users have set a preference for plain-text email only.

Sending multipart alternative messages is a great solution to reach all your subscribers without having to maintain two separate lists.

How It Works

To deliver your marketing messages as multipart/alternative emails, make sure your email marketing software or service provider supports this format. Some service providers create a plain text version of your HTML messages automatically, but it's important to verify the quality of that message.

Usually, you'll compose both a rich HTML version of your message and a plain text equivalent, and then send them together as one multipart alternative message.

The process differs depending on your email marketing software or service, so check the process for your particular tool.

How Does Multipart Alternative Work?

Multipart alternative emails make use of the MIME email standard. The individual parts are sent similarly to attached files, so email programs recognize them as alternative versions. Rather than showing all versions of the email, it displays only the preferred version.

The alternative versions in a multipart/alternative email are separated by a boundary marker, which is identical for all versions.

Each email version also has a MIME content type assigned. This is where the versions differ. With multipart alternative marketing emails, the content types will typically be "text/plain" and "text/HTML."

The types follow each other, and email programs will usually display the last version they're capable of showing. This means "text/plain" followed by "text/HTML" in multipart alternative emails unless users have set a certain preference.

Multipart/Alternative Example

The source of an email using multipart alternative formatting could look like this:

From: Sender <sender@example.com>
To: recipient@example.com
Subject: Example
Date: Fri, 13 Nov 2015 19:36:00 +0000 (GMT)
MIME-version: 1.0
Content-type: multipart/alternative;
boundary="Boundary_MA2"
--Boundary_MA2
Content-type: text/plain; CHARSET=US-ASCII; format=flowed
Content-transfer-encoding: 7BIT
This is but a test.
--Boundary_MA2
Content-type: text/html; CHARSET=US-ASCII
Content-transfer-encoding: 7BIT
<html><body><div><em>This</em> is but a test.</div></body></html>
--Boundary_MA2--