Ha! My Unix timeline history is vague now but I’ve used SCO, DG/UX and HP/UX in anger. Pretty sure mailx was my client on most of those! :) (not to mention SunOS and Sequent at some point. And DRS/NX. But that’s not one to mention in polite company)
Ah, all of thou young fools! Thou haven't not written mail with ink, quill and ye carrier pigeon?
SunOS is most of a decade older than IPoAC, how can you call its users young to a SunOS user?