Buffer overflow in the pop3 service in Hexamail Server 3.0.0.001 Lite allows remote attackers to cause a denial of service (daemon crash) and probably execute arbitrary code via a long USER command.
https://www.exploit-db.com/exploits/4344
https://exchange.xforce.ibmcloud.com/vulnerabilities/36369
http://www.vupen.com/english/advisories/2007/3044
http://www.securitytracker.com/id?1018637