Send emails by a POST request.
Note that all mail fields except body are simply passed directly to SMTP.
Port 465 uses SSL. Other ports are unencrypted. If anyone can give me good reason why TLS or STARTTLS are needed, I can implement them.
Here is the source of this website. This service is implemented in Luan. The entire implemention is in the file send.json.luan. And here is a discussion thread if you want to comment.