run the following command
rpm -grep | sendmail
get that output, eg: sendmail
then run this command
rpm -e sendmail
onec you've deleted sendmail, start looking into postfix. i've writtern a how-to guide for setting up clamAV and postfix on my local LUG website if you can go a path other than sendmail
http://tlug.dnho.net/?q=node/174#comment-184