[Sunhelp] ?: how to protect to be a spaming source

[Wonkyu Chang - Sun Korea SE]

Hi,

I got a customer who have a mail server with sendmail 8.8.7 on solaris 2.6.
He got a warning message that his server was enrolled as spaming host, and was 
asked to get rid of relaying feature on his server.

Could you tell me how to deny the relaying not to be a spaming source?

Thanks for any guidance.
WK Chang