SMTP relay is the entire process of transferring emails involving SMTP servers (or MTAs if you are going to). A relay occurs If your sender and the recipient come from different domains. In practice, even so, the term SMTP relay often refers to SMTP servers that help relaying. Also, There's https://felixjalxh.onzeblog.com/26537176/mailwizz-things-to-know-before-you-buy