While mail servers might be configured to silently discard email, the SMTP RFC strongly discourages this unless senders are recognised being fraudulent or unwanted. For all other mail, the RFC endorses returning undeliverable mail by having an mistake code. Two usually juxtaposed styles are bulk emails and transactional emails. https://dantemuzyd.mdkblog.com/32381606/a-secret-weapon-for-powermtasend-email