Direct deliver cannot be utilised to deliver emails to exterior recipients, by way of example, recipients with Yahoo or Gmail addresses. SMTP relay lets Microsoft 365 or Office 365 relay emails on the behalf by using a connector that's configured using a TLS certificate (recommended) or your public IP handle. https://wavesocialmedia.com/story2556771/the-smart-trick-of-postal-smtp-setup-that-nobody-is-discussing