I have a firstline / graveyard system of Postfix. So, one server is the graveyard of the first line server. I managed this by setting the smtp_fallback_relay in the first line server.
So far, so good, the graveyard receives the emails rejected from the first, but I don't know why, it changes the original message-id of the message. Basically, it makes up a new message-id based on the date and hour, if I'm not wrong.
That's bad, because I'd like to keep track of the messages through this parameter.