Hi there, I've got a strange problem. We have got 3 ISPConfig servers running in VM behind a nat firewall. We use postfix on our server and want to create an MX record for every domain with the hostname mail.domain.com. The problem is that every ispconfig vmguest (even the vmware server) cannot connect to mail.domain.com over port 25, even when the domain is hosted on the same server. telnet: Unable to connect to remote host: Connection refused - But when I try to connect to mail.domain.com from outside (like at home), it works great. The strange thing is, I CAN connect to every ispconfig vmguest using the localhost or hostname of the server, but not the mail.domain.com In local-host-names I've got mail.domain.com, etc.etc. I've looked at the NAT translations, but cannot find anything. Also when I do a telnet on port 80 (www) from a vmguest to a different vmquest, using the public ip adres, it works!!! So It's not a NAT problem or routing problem. It's not a resolving problem, because DNS works perfectly and I can resolve mail.domain.com from every vm server. It's postfix that gives this problem for the vmguests and vmware server. Outside the network everything works the way it should. When I add the record mail.domain.com to /etc/resolv.conf and let it resolve to the local ip of the server or another vmguest, it works also! So you could say it's a NAT problem, but why is www or ftp or dns working through NAT? I've tried the following setting in main.cf mynetworks = 0.0.0.0/0 inet_interfaces = all I need help.... big time!