I have followed: http://www.howtoforge.com/virtual-users-and-domains-postfix-courier-mysql-centos5.1 and http://www.howtoforge.com/how-to-implement-domainkeys-in-postfix-using-dk-milter-centos5.1 When i try to start dk-milter: [root@mexus domainkeys]# service dk-milter start Starting DomainKeys milter (dk-filter #0): dk-filter: smfi_opensocket() failed I tried: chown dk-milt:mail *.pem postfix and dk..... restart but still there is no dk.sock. How can i fix this? I read http://www.howtoforge.com/forums/showthread.php?t=20410 and http://domainkeys.sourceforge.net/policycheck.html says: Testing mexus.org Policy TXT=t=y; o=~ This policy record appears valid. o ~ Domain signs some email t y Domain is in test mode the keys are identical (double checked that). Please help me!