all this bullshit with skype support made me wonder if there was a "falsehoods programmers believe about email addresses" yet. and then i remembered this existed and that i had read it already https://haacked.com/archive/2007/08/21/i-knew-how-to-validate-an-email-address-until-i.aspx/
but i'm going to provide my own much more succinct take on the subject: the only "correct" way to validate an email address is not to.
you might think you know how to validate email addresses, but you don't, so don't do it. seriously, don't