To: test@example.com
From: test@example.com
Subject: Test message with attached message
Message-ID: <8259dd8e-2293-8765-e720-61dfcd10a6f3@example.com>
Date: Sat, 30 Dec 2017 19:12:38 +0100
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:59.0) Gecko/20100101
 Thunderbird/59.0a1
MIME-Version: 1.0
Content-Type: multipart/mixed;
 boundary="------------9B410E80D6DA0868F068B0E4"
Content-Language: en-GB

This is a multi-part message in MIME format.
--------------9B410E80D6DA0868F068B0E4
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit

This is a test message with an attached message.


--------------9B410E80D6DA0868F068B0E4
Content-Type: message/rfc822;
 name="attached-message.eml"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="attached-message.eml"

To: test@example.com
From: test@example.com
Subject: Attached message (plaintext + HMTL, both base64 encoded)
Message-ID: <a30f750d-d56c-8a52-971c-f95a131e8332@example.com>
Date: Sat, 30 Dec 2017 19:31:21 +0100
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:59.0) Gecko/20100101
 Thunderbird/59.0a1
MIME-Version: 1.0
Content-Type: multipart/alternative;
 boundary="------------FAB286B8794CC63C0A0FD1BB"
Content-Language: de-DE

This is a multi-part message in MIME format.
--------------FAB286B8794CC63C0A0FD1BB
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: base64

SGVyZSBpcyB0aGUgYm9keSBvZiB0aGUgYXR0YWNoZWQgbWVzc2FnZS4gU2VhcmNoIGZvciBib2R5T2ZBdHRhY2hlZE1lc3NhZ2VQbGFpbi4=


--------------FAB286B8794CC63C0A0FD1BB
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: base64

PGJvZHk+SGVyZSBpcyB0aGUgYm9keSBvZiB0aGUgYXR0YWNoZWQgbWVzc2FnZS4gU2VhcmNoIGZvciBib2R5T2ZBdHRhY2hlZE1lc3PDpGdlSFRNTC48L2JvZHk+

--------------FAB286B8794CC63C0A0FD1BB--


--------------9B410E80D6DA0868F068B0E4--