Gmail used to have send-as feature that verified only with your ability to click on the link that you get from google on that inbox. Technically you can do the

Gmail used to have send-as feature that verified only with your ability to click on the link that you get from google on that inbox. Technically you can do the same with SES on AWS as well, they verify just a single email address this way (domain is with dns records), and they have SMTP gateways to connect to a mail client .