I use postfix relay smtp server. Rarely send senders to a faulty email address but not send a notification to the sender that the address is wrong, only the letter is in the mail queue.
766AA2133F 46933 Sat Jan 12 19:44:40 from@nobody.tr (connect to mail.somebody.tr[203.188.141.10]:25: No route to host) wrong-email-address@wrong-domain.tr
Why doesn't the sender be notified? which postfix to use for the solution ? thanks, Steven