[CentOS] Spamhaus with Zimbra Mail on CentOS

I realize this is slightly off topic, but I've noticed recently that I've been unable to preform RBL lookups using the the zen and sbl spamhaus RBL lists. Currently using Zimbra Collaboration Suite using CentOS 5 I'm seeing logs showing the following output.

[root at phantom ~]# cat /var/log/zimbra.log | grep spamhaus
Jul 18 13:07:12 phantom postfix/smtpd[27001]: warning: 107.178.203.192.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=107.178.203.192.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:07:19 phantom postfix/smtpd[27001]: warning: 22.178.203.192.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=22.178.203.192.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:09:11 phantom postfix/smtpd[28886]: warning: 107.178.203.192.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=107.178.203.192.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:09:16 phantom postfix/smtpd[28886]: warning: 22.178.203.192.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=22.178.203.192.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:15:52 phantom postfix/smtpd[32148]: warning: 202.200.26.72.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=202.200.26.72.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:18:25 phantom postfix/smtpd[1093]: warning: 26.93.98.14.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=26.93.98.14.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:19:29 phantom postfix/smtpd[1093]: warning: 202.200.26.72.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=202.200.26.72.zen.spamhaus.org type=A: Host not found, try again
Jul 18 13:25:51 phantom postfix/smtpd[4399]: warning: 202.200.26.72.zen.spamhaus.org: RBL lookup error: Host or domain name not found. Name service error for name=202.200.26.72.zen.spamhaus.org type=A: Host not found, try again



After doing some reading I've tried a number of DNS servers ( thinking the issue may have been DNS poisoning )  all of which appear to be unable to preform dig lookups the spamhaus hosts. Is anyone else seeing similar results?