@HoldToTheRod I wouldn't use the word "recognise" as opposed to "differentiate", because to me the former incorporates the knowledge that the source is the source, but maybe we mean the same thing.
#2 is good, but I wouldn't say it all hinges on that. #3 should be verified independently.
Maybe I should've used a more realistic example of text chatting with someone online (because who gets phone calls any more) and them claiming to be Jeff Bezos. Or, purely hypothetically, getting an email from someone claiming to be a Nigerian prince. Or some scammer on a dating site who isn't claiming to…