Configure Mailing Server wanted

we need to configure mailing server on a server with these specifications : Centos 5 Server with 2 specified Ip Adresses OS installed : Linux [login to view URL] Postfix enabled opendkim installed but didnt work with spf record on dns domain Key enabled open relay disabled what we need to do is to enable the dkim check to all the outgoing check and to enable signing outgoing mail in all the domains . we have a plesk 10 Installed and open dkim also but it has problems to start You have the choice to work on postfix or another MTA. The Important is to enable for each domain mails (old or new ones that we can add ) spf ,DomainKeys, DKIM and sender id . We have the project to send around 1,4 million email per month. Regards, Albert