Technically valid e-mail addresses - but nonsensical ones. I haven't seen an e-mail without a domain cross a network in decades ("cross a network" excepts "user

Technically valid e-mail addresses - but nonsensical ones. I haven't seen an e-mail without a domain cross a network in decades ("cross a network" excepts "user@localhost", and I'm not old enough to have seen any IP-adressed mails ;)). So yes, I believe that in 2016, a match on ^[^@]+@([^.@]+\.)+[^.@]+\.?$ does not have any actual false negatives, although allowing false positives. That's not entirely helpful in this CVE, though.