Unknown versions of Symantec Norton AntiVirus and Microsoft Outlook allow attackers to cause a denial of service (crash) via malformed e-mail messages (1) without a body or (2) without a carriage return ("\n") separating the headers from the body.
http://www.securityfocus.com/bid/11259
http://www.securityfocus.com/archive/82/376487/2004-09-24/2004-09-30/0