Secure Email Relays with SMTP Authentication
Where: This change applies to Salesforce Classic and Lightning Experience in Professional, Enterprise, Performance, Unlimited, and Developer editions.
How: In Email Relays in Setup, create an email relay, and enable the SMTP authentication setting.
Before enabling SMTP authentication, test this feature in a sandbox org to ensure that it works as expected with your email relay. Some email services don’t support SMTP authentication for email relays.