From: sender@example.com To: recipient@example.com Subject: Example Multipart/Alternative Email Message-ID: <1234567890@example.com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="boundary123" --boundary123 Content-Type: text/plain; charset="UTF-8" This is a simple email message. --boundary123 Content-Type: text/html; charset="UTF-8"

This is a simple email message.

--boundary123--