Zawinski's Law of Software Envelopment, also known as Zawinski's Law, states: Every program attempts to expand until it can read mail.
I assumed it meant to send the output of the command as mail. That's vaguely useful instead of piping to a cmdline MUA. I couldn't believe I'd been missing this for 30 years and so I tried it on few things like
ps aux --mail=me@domain
error: unknown gnu long option
Looked in my inbox. Nothing.
Then I got to the bottom of the page for the punchline.
grrrr