Over a year ago, I put together my current production server. It was largely an exercise in learning Linux. With a lot of trial and error, this machine has been working quite nicely for about 18 months. That server was assembled using several excellent How To's on this site which I am very grateful. Since putting that server into production, I have acquired newer and better hardware, learned more about RAID, LVM and Xen. This new machine is now ready for production which is where my new questions arise. I plan on having a Xen DomU machine be the new production server which I plan to run Debian Lenny and ISPConfig3 on it. I have two public IP addresses. The current production server is currently on one of the public IP addresses. My provider handles the reverse DNS entries for my IP addresses. Currently, they are both set to [sanitized] mail.example.com. Just for the record, it is not really example.com, but rather my actual domain name. The new server will reside on the other public IP address. For some period of time, both will be in existence and will need to coexist. I am not really concerned about any of the other server functions other than email during the switch. My current production email server has a local hostname that is not made public through DNS. Postfix was configured to use the same FQDN as the reverse DNS entry at my ISP. Can I install ISPConfig in a similar manner where the machine FQDN is different than the FQDN used by Postfix? Or should I build the new DomU (and all services) with the FQDN that is associated with the reverse DNS entry? Should I have my ISP change the reverse DNS entry for the second public IP address to be something unique and different from the other address?