Hello:
This may not be the right forum for this, but over the weekend I tried to replace my PIX515e with a new ASA5520. I got it online and then right away in testing when sending outbound e-mails I got the below NDR. I use Exchange. It goes Back End to Front End and then forwarded to a delivery service (ProofPoint). I assumed if I would have had delivery problems messages would just have queued up rather than users getting an NDR. After unsuccessfully trying to resolve the issue I had to revert back to the PIX515e. When I did that I was not getting NDR's anymore, but NAT's and e-mail were not working. I ended up flushing the ARP cache on my upstream router and then everything returned to normal.
Could a bad ARP entries on my upstream router caused NDR's like what I saw?
******************* NDR *******************
Your message did not reach some or all of the intended recipients.
Subject: How are you
Sent: 8/8/2010 3:54 PM
The following recipient(s) cannot be reached:
xyz@gmail.com on 8/8/2010 3:54 PM
You do not have permission to send to this recipient. For assistance, contact your system administrator.
<SERVER.DOMAIN.COM #5.7.1 smtp;550 5.7.1 Unable to relay for xyz@gmail.com>
Harrison Midkiff
