Premium Antispam in Symantec Mail Security for Domino Server 5.1.x before 5.1.2.28 does not filter certain SMTP address formats, which allows remote attackers to use the product as a spam relay.
https://exchange.xforce.ibmcloud.com/vulnerabilities/29676
http://www.vupen.com/english/advisories/2006/4118
http://www.securityfocus.com/bid/19866
http://securitytracker.com/id?1017094
http://securityresponse.symantec.com/avcenter/security/Content/2006.10.19.html