Email authentication has had a turbulent history - SMTP did not have a native form of authentication when it was designed, and all modern authentication methods are built on top of that system. This was not a problem in the 1980s because there were simply too few people emailing - the only ones using it were universities and corporations actively involved in building the internet. Since then we’ve got a variety of tools to attempt to verify emails, including SPF, DKIM, and DMARC, and I wanted t...