In this case, the getting server can notify you of troubles employing SMTP error codes, and being aware of whatever they signify helps you diagnose and take care of email supply roadblocks. For instance, Here's two groups of SMTP mistakes that crop up typically: And there you've got it! https://www.peopleperhour.com/hourlie/setup-bulk-email-server-or-unlimited-smtp-with-powermta/468306