100% agreed here. Accept a text field; maybe validate that it has an @ in it and a . after the @. Send that address a confirmation email. Now you've got consen

100% agreed here. Accept a text field; maybe validate that it has an @ in it and a . after the @. Send that address a confirmation email. Now you've got consensual opt-in and you've somewhat protected yourself from adding a wrong address to your recurring mailing list. Prevent abuse with long (seconds) delays between submissions from the client. If the user thinks they did it right, they're waiting on their email inbox anyway; if they immediately realize they made a typo, it'll take 2-3s to fix. The RFCs were written when manually (not from cron) sending email to another user on your local system as a thing that actually happened. I'm certain you actively want to avoid that now.