Hello, I am managing a Postfix mail relay service in our internal network. The relay itself is more permissive than the downstream SMTP server. So it is possible, and indeed it regularly happens, that my relay accepts a message which is subsequently bounced by the downstream server. There is no way to inform the original sender what happened to the message after the relay accepted it.
Is it possible to delay closing the SMTP connection from the original sender until the response from the downstream server is received, and then respond accordingly in the original connection? I could imagine this would imply some complications in terms of performance, and the question what happens if downstream is not available. But in the way it would appear the advantage of telling the original sender what happened to a message, outweighs the disadvantages. Regards, Lucas
