The following recipient(s) cannot be reached:
email@example.com on 12/19/2011 9:56 AM
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.
< AZ25EGS03.xxx.com #5.0.0 smtp; 5.1.0 - Unknown address error 550-'5.7.1 <firstname.lastname@example.org>... Relaying denied. IP name lookup failed [0.0.0.0]' (delivery attempts: 0)>
Would the above error message be a IP lookup issue our mail server is having with the recipient server ip address?