SMTP is short for Simple mail transfer protocol. It's really a networking procedure that allows your Pc to send out emails to other recipient email clientele like Gmail, outlook, yahoo, etc via the internet. it is so simple as that. With DNS intense destructive caching, as explained in RFC8198, https://virtualizationsupport88888.activosblog.com/26411260/the-fact-about-azure-support-that-no-one-is-suggesting