It's nobody else's business whether the emails in your inbox are valid or not, and that's basically all non-deniable DKIM signatures do: durable secure verifiable DKIM signatures are "security feature" with real-world value exclusively for attackers.
If you’re under Rule 26 discovery or disclosure requirements, it absolutely might be my business whether emails in your client are valid, but I suppose you could classify opposing counsel as an “attacker,” so you’re not wrong.
I get the verification the email actually came from the domain (i.e., someone, who has the credentials of an insider) vs. an email that was totally spoofed, from the outside, without any creds of the purported sender org. (Right?)
Hands on keyboard? You're right, absolutely not. But I can learn something useful via DKIM nevertheless.
