Hello, I had setup a vps with the CentOS Apache installed. I am facing a problem with postfix, I can send & receive emails without problem but I got the bounced back emails in mail log. For your information, I have the port 25,110,587,993,995 opened on firewall and I also could telnet the host like google, yahoo on port 25. PTR & rDNS also been set and I had checked my IP at mxtoolbar.com, it is not being blacklisted. Below are the info of postconf -n. What could be causing this problem??