STARTTLS cannot be enforced. It will be used automatically if the mail server supports it. The encryption type should be set to ‘None/STARTTLS’ in this case. See here for an example on how to configure self signed certificates. — which was reportedly seized last July after a surprising effort by https://bbs.pku.edu.cn/v2/jump-to.php?url=https://www.autofreshshop.com/