消息头的区别：Content-Type: charset="UTF-8" 和 Content-Transfer-Encoding: 8bit

Question

I had received some mail message, but I was confused with these headers:

Content-Type: text/plain;
    format=flowed;
    charset="UTF-8";
    reply-type=response
Content-Transfer-Encoding: 8bit

If Content-Type: charset="UTF-8" is already specified, so why we need Content-Transfer-Encoding: 8bit ?

Answer 1

Because you can also have:

Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: base64

The charset is independent of the content encoding.