A comment from the presenter from Youtube: Unfortunately, after I did some further investigation, it seems that some of the slides in my presentation here are

A comment from the presenter from Youtube: Unfortunately, after I did some further investigation, it seems that some of the slides in my presentation here are wrong. I took some information from the "Email address" Wikipedia page, which turned out to have incorrect info, and in one I just misunderstood the rules (the "local@domain(comment)" part, which is invalid). I have since amended the presentation, but the general point of this video of how to do validation still stands.