Sendmail 8.12.0 through 8.12.6 truncates log messages longer than 100 characters, which allows remote attackers to prevent the IP address from being logged via a long IDENT response.
http://www.securityfocus.com/bid/5770
http://www.iss.net/security_center/static/10153.php
http://archive.cert.uni-stuttgart.de/bugtraq/2002/09/msg00267.html