cpython/Lib/test/test_email/data/msg_42.txt

Content-Type: multipart/mixed; boundary="AAA"
From: Mail Delivery Subsystem <[email protected]>
To: [email protected]

This is a MIME-encapsulated message

--AAA

Stuff

--AAA
Content-Type: message/rfc822

From: [email protected]
To: [email protected]
Content-Type: multipart/mixed; boundary="BBB"

--BBB--

--AAA--