While a good deal of our entertainment circa 1993 (Computer Science Honours, Sydney University) centered around exploiting this delightful fact (close second: unattended terminals), I had long since figured that forging emails off a open SMTP port wasn't really still A Thing.
Oh, it most definitely still is A Thing. There have been a few notable attempts to stop it happening, but none of them have really worked completely, and they only apply to some from-domains.
