Return-Path: <return@example.com>
From: Sender <sender@example.com>
To: <recipient@example.invalid>
Subject: Email with embedded message
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="----------=_4F506AC2.EE281DC4"
Message-Id: <9181f493-df49-4af5-8ad2-e1a8eb692a98>
Date: Wed, 15 Jul 2020 19:48:41 +0100

This is a multi-part message in MIME format.

------------=_4F506AC2.EE281DC4
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit

Example outer message.
Example second line.


------------=_4F506AC2.EE281DC4
Content-Type: message/rfc822; x-spam-type=original
Content-Transfer-Encoding: 8bit

From: "Embed sender" <embed@example.com>
To: <rcpt2@example.invalid>
Subject: Embedded subject line
Date: Wed, 15 Jul 2020 12:34:56 +0000

Example embedded message.
Second line.

------------=_4F506AC2.EE281DC4--