Multiple heap-based buffer overflows in the POP3 server in Alt-N Technologies MDaemon before 9.0.6 allow remote attackers to cause a denial of service (daemon crash) and possibly execute arbitrary code via long strings that contain '@' characters in the (1) USER and (2) APOP commands.
https://www.exploit-db.com/exploits/2245
https://exchange.xforce.ibmcloud.com/vulnerabilities/28517
http://www.vupen.com/english/advisories/2006/3361
http://www.securityfocus.com/archive/1/444015/100/0/threaded
http://securitytracker.com/id?1016729
http://securityreason.com/securityalert/1446