Verify Unknown source Email ID
We have configured SMTP Mail relay Server in our local network. I have allowed one system from Relay Server to send mail from application. But one drawback is that, if I used any unknown Email ID (not exist or created in our domain) to send mail from application to valid Email Address; and it successfully delivered (Not giving error such as, Source Mail Id is not valid).
For eg., I have not created any User Email ID or Group Email ID or alias in our domain like firstname.lastname@example.org. It is unknown (not exist) Email ID. But when I used this email ID in application to send mail regarding setup. Then mail successfully delivered to destination Id from email@example.com.
Can we restrict to send mail only from valid/known Email IDs which are created in our Domain?
Source E-Mail Id should verify before sending mail.
Can we do any setting from Relay server or Admin Console to verify source E-Mail ID?