encode problem of kmail for Japanese Mail

Hello,

As you probably know, for Japanese-language emails contain, there are
three types of character codes

1. ISO-2022-jp
2. UTF-8
3. Shift_JIS

Here, kmail decodes ISO-2022-JP-coded e-mails correctly, but cannot
 decode  UTF-8-coded e-mails or Shift_JIS coded -e-mails correctly,
 and the mail becomes garbled and cannot be read at all.

However, with "kmail --msg e-mail", the source of the e-mails is correctly
displayed.

I have confirmed this with;

1. openSUSE Leap 15.1 -- kmail 18
2. openSUSE Leap 15.4 -- kmail 22
3. openSUE Tumbleweed -- kmail 22

There exits a bug in kmail, I think.

FYI, the original e-mail;

 https://drive.google.com/file/d/1TOoiJwtD8_GNX-9Nkt93zHt23kJU_0eM/view?usp=share_link

the correct view with the e-mail client:

https://drive.google.com/file/d/1iYkdD6iLi20uswQpgzjZylk6XQXfKfWs/view?usp=share_link

and, kmail's view in my environment;

https://drive.google.com/file/d/1iYkdD6iLi20uswQpgzjZylk6XQXfKfWs/view?usp=share_link

Any idea?

Thanks, in advance.

---
    Masaru Nomiya               mail-to: nomiya @ galaxy.dti.ne.jp

  "A society bound by e-mail and mobile phones deprives us of the
	  freedom to face ourselves and indulge our fantasies."
	  
                                       -- Michael Crichton (Speech in Japan) --