Every major email provider and sender already does that. That's table stakes, along with a dozen other things, that's required or else your network will be 99%

Every major email provider and sender already does that. That's table stakes, along with a dozen other things, that's required or else your network will be 99% spam (if it gets any kind of volume, that is). See https://blog.mailchimp.com/where-spam-traps-come-from-and-how-they-work/ https://blog.mailchimp.com/where-spam-traps-come-from-and-ho...