Nobody really wanted a generic engine, they wanted an smtp engine No, when sendmail was king of the hill, the whole world wasn't SMTP, so being able to mung a

Nobody really wanted a generic engine, they wanted an smtp engine No, when sendmail was king of the hill, the whole world wasn't SMTP, so being able to mung addresses 'generically' and deliver messages between wildly different, non-RFC822 schemes was critical functionality. Sure, that's not how things are now, but you have to consider the context when it was created.