The key word being those that knew him. He wasn't famous for things so strangers wouldn't have done that, and I think if this were a fake email, then sending it to a high profile person would be more of a stranger activity than an associate.

I don't think an Epstein associate would send a fake email like that, as it would be more likely to blow back on them than implicate Epstein any further than he was already implicated.

So yeah, this email seems a credible thing and consistent with Epstein. Also I would not suspect a fake header if we knew the sender, so I'd think the sender could be presumed not to be a victim of spoofed headers too.