Tangentially related - I would pay for an email service with an off-site delivery for Gmail recipients. Basically, it should hold any email that is to be sent

Tangentially related - I would pay for an email service with an off-site delivery for Gmail recipients. Basically, it should hold any email that is to be sent to GMail servers and instead send a note saying "You've got mail, pick it up here https://<url> https://<url>. Anything like this out there?