To: test@example.com
From: test@example.com
Subject: 3-third-subject
Content-Type: multipart/mixed;
 boundary="------------2E5D78A17C812FEFF825F7D5"

This is a multi-part message in MIME format.
--------------2E5D78A17C812FEFF825F7D5
Content-Type: text/plain; charset=iso-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

3-third-content
--------------2E5D78A17C812FEFF825F7D5
Content-Type: message/rfc822;
 name="2-second-email.eml"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="2-second-email.eml"

To: test@example.com
From: test@example.com
Subject: 2-second-subject
Content-Type: multipart/mixed;
 boundary="------------9919377E37A03209B057D47F"

This is a multi-part message in MIME format.
--------------9919377E37A03209B057D47F
Content-Type: text/plain; charset=iso-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

2-second-content
--------------9919377E37A03209B057D47F
Content-Type: message/rfc822;
 name="1-first-email.eml"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="1-first-email.eml"

To: test@example.com
From: test@example.com
Subject: 1-first-subject
Content-Type: multipart/mixed;
 boundary="------------0919377E37A03209B057D47A"

This is a multi-part message in MIME format.
--------------0919377E37A03209B057D47A
Content-Type: text/plain; charset=iso-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

1-first-content
--------------0919377E37A03209B057D47A
Content-Type: message/rfc822;
 name="0-zero-email.eml"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="0-zero-email.eml"

To: test@example.com
From: test@example.com
Subject: 0-zero-subject
Content-Type: text/plain; charset=iso-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

0-zero-content
--------------0919377E37A03209B057D47A--

--------------9919377E37A03209B057D47F--

--------------2E5D78A17C812FEFF825F7D5--