Return-Path: test@test.com
From: TEST <test@test.com>
To: Me <me@me.me>
Subject: multipart/alternative with nested rfc822
MIME-Version: 1.0
Date: Mon, 01 Jan 2024 00:00:00 +0000
Message-ID: <alternative-nested-rfc822@test.com>
Content-Type: multipart/mixed; boundary="=-outer="

--=-outer=
Content-Type: multipart/alternative; boundary="=-alt="

--=-alt=
Content-Type: text/html; charset="UTF-8"

<html><body>HTML only content - the sibling related has no text alternative</body></html>

--=-alt=
Content-Type: multipart/related; boundary="=-related="

--=-related=
Content-Type: image/png; name="spacer.png"
Content-Transfer-Encoding: base64

iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==

--=-related=--

--=-alt=--

--=-outer=
Content-Type: message/rfc822; name="attached.eml"

Return-Path: inner@test.com
From: Inner <inner@test.com>
To: Me <me@me.me>
Subject: Inner message
MIME-Version: 1.0
Date: Mon, 01 Jan 2024 00:00:00 +0000
Message-ID: <inner@test.com>
Content-Type: multipart/alternative; boundary="=-inner-alt="

--=-inner-alt=
Content-Type: text/plain; charset="UTF-8"

This is the plain text version of the inner message.

--=-inner-alt=
Content-Type: text/html; charset="UTF-8"

<html><body>This is the HTML version of the inner message.</body></html>

--=-inner-alt=--

--=-outer=--
