I followed directions and i almost have dk-filter operational on a centos machine Heres the problem though I start the dk-filter through a custom startup script as shown here: [root@lunar ~]# service domainkeys start Starting dk-filter: [ OK ] [root@lunar ~]# This is what I get in sendmail maillog (most signifigant error shown in bold): Apr 5 13:12:59 lunar dk-filter: Sendmail DomainKeys Filter v1.0.2 starting (args: -l -p inet:8891@localhost -c simple -d nuper.com -s /var/db/domainkeys/mail.key.pem -S mail -u dkim -M MSA) --- email sent here --- fujinet.net>, proto=SMTP, daemon=MTA, relay=ip-77.net-89-2-209.rev.numericable.fr [220.127.116.11] Apr 5 13:13:21 lunar sendmail: n35KCRU2022167: Milter (dk-filter): write(L) returned -1, expected 47: Broken pipe Apr 5 13:13:21 lunar sendmail: n35KCRU2022167: Milter (dk-filter): to error state This is what I have added to sendmail.mc and recompiled: [root@lunar mail]# cat sendmail.mc|grep dk-filter INPUT_MAIL_FILTER(`dk-filter', `S=inet:8891@localhost')dnl [root@lunar mail]# Any information on how to solve the elusive "Broken pipe" error is appreciated. I also had this error using it as a unix: sock in /var/run/dk-filter/dk.sock and as a local: sock on both the dk-filter side and the sendmail.mc side.. Nothing works, broken pipe every time. Thanks PS This is dk-milter-1.0.2.tar.gz downloaded off of Sourceforge. I thought this was perhaps a software problem, maybe a bug in the dk-filter program So I tried dk-milter-1.0.1.tar.gz from late 2008 Same problem!