Ipswitch IMail Server 2006 before 2006.21 allows remote attackers to cause a denial of service (daemon crash) via unspecified vectors involving an "overwritten destructor."
http://www.vupen.com/english/advisories/2007/2574
http://secunia.com/advisories/26123
http://docs.ipswitch.com/IMail%202006.21/ReleaseNotes/IMail_RelNotes.htm#NewRelease