Hi: I'm very new to this community. My heartiest thanks to the wonderful how-to's (The Perfect Server - CentOS 6.3 x86_64 (nginx, Courier, ISPConfig 3)), which helped me a lot to install and configure my Web/DNS/Mail/MySQL server without major issues. Everything works as expected except I cannot connect to my mail server using Outlook or other email client. But the webmail (squirrelmail) works and I can send/receive emails (using a relayhost). Here is some detail of the system (domain/ip is not actual): I have everything installed in the same server. Hostname: websvr fullname: websvr.xyz.com Private IP: 192.168.1.11 (I have NAT in my router and ext IP 58.97.xxx.xx) There is a MX entry in DNS zone for mail.xyz.com and I can ping to that. I can telnet to the port 25 using only hostname (websvr) or local IP (192.168.1.11) but unable to telnet mail.xyz.com 25. Any help will be greatly apprecieted.