Earlier this morning you may have received the following error while relaying through ExchangeDefender:

< outbound2.exchangedefender.com #5.7.1 SMTP; 550 5.7.1 … Access denied to by new.spam.dnsbl.sorbs.net DNSBL (http://dnsbl.sorbs.net/)>

This issue has been corrected and mail is flowing through correctly. If you received this error please resend the message as it was permanently rejected by the recipients mail server.