If you are writing Gmail no one is sending to foo@localhost. It’s a typo.
(And you certainly don’t want to send every bcc a verification email they have to click on!)
(And you certainly don’t want to send every bcc a verification email they have to click on!)
That neither solution proposed upthread - double inputs, or a verification email - is as user-friendly as catching "oops you forgot a dot" validation on the field in an email client.
To put another way, as anecdotal experience I've encountered many forms online that won't accept my email address or phone or whathaveyou because of buggy validation. I can't recall when I mistyped my email, but surely it's possible I've done it at some point, however the difference is in the price I pay. If I mistype my email and don't get a confirmation email or w/e I can always try signing up again. However if I can't use the form because the validation is bugged there is no straightforward recourse I can take as a user.