Even though mail servers is often configured to silently discard email, the SMTP RFC strongly discourages this Except senders are identified being fraudulent or undesirable. For all other mail, the RFC recommends returning undeliverable mail having an mistake code. Two generally juxtaposed styles are bulk emails and transactional emails. https://cashgsfqe.timeblog.net/62493022/top-guidelines-of-bulk-email-blast