I know that there are a lot of tutorials on how to do this but not any that are easy at first sight.
Let’s get right into it
Open up your servers shell environment and do the following below
nano /etc/hosts
nano /etc/hostname
nano /etc/postfix/main.cf
cd /etc/pve/nodes/
cp -r old new
rm -r old
cd /var/lib/rrdcached/db/pve2-node/
cp -r old new
rm -r old
Credit to apmuthu on the Proxmox Forum
Hope this helps!