I found that in my postfix, the bounced mails that return to senders have 'Return-Path: <>', if the mails come from internet, this make the failures of "returning to sender", because:
"You are not authorized to send mail as <>"
"invalid user - <> SIZE=2509"
I'm not clear about the meaning of 'Return-Path', is there anyone can give me an explanation?
I explored the mailbox, and found:
From MAILER-DAEMON Wed Dec 28 09:54:39 2005
Received: by USER@SITE.com (Postfix)
id 166EBF14086; Wed, 28 Dec 2005 09:54:39 +0800 (CST)
Date: Wed, 28 Dec 2005 09:54:39 +0800 (CST)
From: MAILER-DAEMON@SITE.com (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
Content-Type: multipart/report; report-type=delivery-status;
This is a MIME-encapsulated message.
This site has a valid DNS name. I don't know why it becomes user <> since there is "From: MAILER-DAEMON@SITE.com (Mail Delivery System)"
Some mails were bounced by the remote server, and I found that the 'Return-Path' of the message which my server sent is right(USER@SITE.com). Why?