Originally Posted by DJManas
I am kinda newbie at this could you give me more details how i should do that?
Sorry, I've been AFK for a few days.
You need to decide what name you want for your mail server, then have only one reverse DNS record (PTR) that points at that name, not the list of records like I quoted. Then, make the forward (A) record be that name. Also, when your server connects to other servers, it announces its name to the other server. You should make sure your server announces itself as whatever name you choose for your forward DNS record. That three way relationship is what spam many filters look for. You don't need any more DNS records than this to run a mailserver that sends and receives email for multiple domains. You can think about SPF and domain keys, but they are not required for a functioning mail server.
Hope that helps.