Recently our email domain/Public IP address has been blacklisted on two separate occasions over the past 3 weeks on two different black lists which caused outgoing/external email to get bounced. Incoming email seemed to be unaffected.
On the most recent occasion we got added to one black list on Friday and I got us removed on Saturday, but we are still getting a small number of emails that are being bounced back and not sure why - any ideas?. Im concerned we may get added again if we dont find out the cause of the issue. We are currently running SBS 2003 as our email server and have a Sonicwall email security/Spam appliance that filters email. We have AVG anti-virus installed on all servers and client computers.
Is there any way to find out why we got onto the blacklists in the first place?, any software tools available? Also really want to prevent us from getting onto any black lists in the future.
Two Example NDR’s we have received are the following:
The following recipient(s) cannot be reached:
firstname.lastname@example.org on 17/10/2011 13:38
This message was rejected due to the current administrative policy by the destination server. Please retry at a later time. If that fails, contact your system administrator.
<mail.wisdom.ltd.uk #5.3.2 smtp;554 mx.ptn-ipin04.plus.net Your access to this mail system has been rejected due to the sending MTA's poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.>
The following recipient(s) could not be reached:
email@example.com on 17/10/2011 16:55
The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.
<mail.wisdom.ltd.uk #5.0.0 smtp;550 Invalid recipient <firstname.lastname@example.org > (#5.1.1)>