IBM AIX 5.2 and earlier distributes Sendmail with a configuration file (sendmail.cf) with the (1) promiscuous_relay, (2) accept_unresolvable_domains, and (3) accept_unqualified_senders features enabled, which allows Sendmail to be used as an open mail relay for sending spam e-mail.
https://exchange.xforce.ibmcloud.com/vulnerabilities/11993
http://www.securityfocus.com/bid/7580
http://www.kb.cert.org/vuls/id/814617
http://security.sdsc.edu/advisories/2003.05.13-AIX-sendmail.txt