550 Error for local domain insteasd of Mail Delivery Failure email messag

Hi, I have this issue (i can't name it problem): When sending emails to a deleted email address from an external email, the external email receives back a "Mail delivery failed" email with the 550 error. This is normal as long as the Default Adress in cPanel is set to " :fail: No Such User Here ". The issue i have is that when someone on that server is sending an email to a non existing email address on the same server (or the same domain), they don't receive back the "Mail delivery failed" email. What they see is an "on-screen" error in the email client or on webmail, instead of an email message. What can i do in order to also have local email accounts to receive the "Mail delivery failed" email with the 550 error when sending emails to local non-existent email addresses? Thanks.