// Build a simple text message with a single attachment
    let mut message = MessageBuilder::new();
    message.from(("John Doe", "[email protected]").into());
    message.to("[email protected]".into());
    message.subject("Hello, world!".into());
    message.text_body("Text body contents go here.");
    message.binary_attachment("image/png", "image.png", &[1, 2, 3, 4]);

    // Write message to memory
    let mut output = Vec::new();
    message.write_to(&mut output).unwrap();

    // Build a multipart message with text and HTML bodies,
    // inline parts and attachments.
    let mut message = MessageBuilder::new();
    message.from(("John Doe", "[email protected]").into());

    // To recipients
    message.to(vec![
        ("Antoine de Saint-Exupéry", "[email protected]").into(),
        ("안녕하세요 세계", "[email protected]").into(),
        ("Xin chào", "[email protected]").into(),
    ]
    .into());

    // BCC recipients using grouped addresses
    message.bcc(
        vec![
            (
                "My Group",
                vec![
                    ("ASCII name", "[email protected]").into(),
                    ("ハロー・ワールド", "[email protected]").into(),
                    ("áéíóú", "[email protected]").into(),
                    ("Γειά σου Κόσμε", "[email protected]").into(),
                ],
            )
                .into(),
            (
                "Another Group",
                vec![
                    ("שלום עולם", "[email protected]").into(),
                    ("ñandú come ñoquis", "[email protected]").into(),
                    "[email protected]".into(),
                ],
            )
                .into(),
        ]
        .into(),
    );

    // Set RFC and custom headers
    message.subject("Testing multipart messages".into());
    message.in_reply_to(vec!["message-id-1", "message-id-2"].into());
    message.header(
        "List-Archive",
        URL::new("http://example.com/archive").into(),
    );

    // Set HTML and plain text bodies
    message.text_body("This is the text body!\n");
    message.html_body("
HTML body with \"my-image\"/>!
");

    // Include an embedded image as an inline part
    message.binary_inline("image/png", "my-image", &[0, 1, 2, 3, 4, 5]);

    // Add a text and a binary attachment
    message.text_attachment("text/plain", "my fíle.txt", "Attachment contents go here.");
    message.binary_attachment(
        "text/plain",
        "ハロー・ワールド",
        b"Binary contents go here.",
    );

    // Write the message to a file
    message
        .write_to(File::create("message.eml").unwrap())
        .unwrap();

    // Build a nested multipart message
    let mut message = MessageBuilder::new();

    message.from(Address::new_address("John Doe".into(), "[email protected]"));
    message.to(Address::new_address("Jane Doe".into(), "[email protected]"));
    message.subject("Nested multipart message".into());

    // Define the nested MIME body structure
    message.body(MimePart::new_multipart(
        "multipart/mixed",
        vec![
            MimePart::new_text("Part A contents go here...").inline(),
            MimePart::new_multipart(
                "multipart/mixed",
                vec![
                    MimePart::new_multipart(
                        "multipart/alternative",
                        vec![
                            MimePart::new_multipart(
                                "multipart/mixed",
                                vec![
                                    MimePart::new_text("Part B contents go here...").inline(),
                                    MimePart::new_binary(
                                        "image/jpeg",
                                        "Part C contents go here...".as_bytes(),
                                    )
                                    .inline(),
                                    MimePart::new_text("Part D contents go here...").inline(),
                                ],
                            ),
                            MimePart::new_multipart(
                                "multipart/related",
                                vec![
                                    MimePart::new_html("Part E contents go here...").inline(),
                                    MimePart::new_binary(
                                        "image/jpeg",
                                        "Part F contents go here...".as_bytes(),
                                    ),
                                ],
                            ),
                        ],
                    ),
                    MimePart::new_binary("image/jpeg", "Part G contents go here...".as_bytes())
                        .attachment("image_G.jpg"),
                    MimePart::new_binary(
                        "application/x-excel",
                        "Part H contents go here...".as_bytes(),
                    ),
                    MimePart::new_binary(
                        "x-message/rfc822",
                        "Part J contents go here...".as_bytes(),
                    ),
                ],
            ),
            MimePart::new_text("Part K contents go here...").inline(),
        ],
    ));

    // Write the message to a file
    message
        .write_to(File::create("nested-message.eml").unwrap())
        .unwrap();