Date: Sun, 24 Nov 2019 21:13:45 -0500 Subject: test message Message-ID: From: Alice To: Bob Content-Type: multipart/mixed; boundary="xyz" --xyz Content-Type: multipart/alternative; boundary="abc123" --abc123 Content-Type: text/plain This is a simple message --abc123 Content-Type: text/html

This is a simple message

--abc123-- --xyz Content-Type: text/plain Content-Disposition: attachment; filename="test.txt" This is a simple attachment file.