a email auto receive script (for gmail). By IMAP to get your unread email set. And go throught all item in set, check whether email's subject can match rule. if match, then will receive content.html to sender.
so you need a email and turn on IMAP and smtp.
set your receive content in content.html.
because my project will run in action. so you need to config your gmail as a gobal ENV in Settings.
ps: action config see action.yml