SORBS Aggregate zone (proxies) identified this IP address or domain as sending spam.
This could be because of a virus, bad software, or misconfigured mail server. SORBS Aggregate zone (proxies) thinks spam senders should be stopped, but safe IPs and domains should be allowed.
You can learn more about SORBS Aggregate zone (proxies) delisting by visiting their website: http://www.sorbs.net/lookup.shtml