Installing OpenDKIM:
yum install opendkim
Create private and public key:
mkdir /etc/opendkim/keys/myhostname.lt /usr/sbin/opendkim-genkey -D /etc/opendkim/keys/myhostname.lt/ -d myhostname.lt -s default chown -R root:opendkim /etc/opendkim/keys/myhostname.lt chmod 640 /etc/opendkim/keys/myhostname.lt/default.private chmod 644 /etc/opendkim/keys/myhostname.lt/default.txt