From "http://www.orbs.org/otherresources.cgi", we find that: Linuxconf users beware! - Linuxconf was found to be generating faulty (old) check_rcpt tables as recently as 20 July 1999. Make sure your version is newer than this before using it to generate sendmail.cf files. As a result, using linuxconf opens you to acting as an open smtp relay. My site is getting hit hard by the spammers...
Added Jacques to CC line
1.16r10-2 released, which should fix this.