It is a known fact, that all SMTP-traffic today must have valid digital signature in it. Most major email providers won't even process your mail without one and all of them will classify your precious as junk. So, must have DKIM.
Meanwhile I find it weird that mail client's don't display DKIM verification status as receiving SMTPd added to mail headers. Gmail kinda does, but you'll have to click to see the "original" mail. Outlook and such won't display any information. As a negative, iOS will display "sender verified" to an email having properly valid DMARC in it.
Complaining here about lack of features is an option. I chose the hard way: https://github.com/roundcube/roundcubemail/pull/10222
Now there is a DKIM validator plugin to parse mail headers and display the validation status against alleged sender domain.
Example:
(https://i.postimg.cc/vHVVvP9S/image.png)
Now it is pretty easy for end-user to determine if email sender is a forgery, valid or uncertain.
Any comments, feedback or improvement ideas are welcome.