After I modified the hostname in /etc/hosts or the Control Centre GUI, the SENDMAIL reported a failure said that 'hostname not find' when rebooting, I had to modify the hostname back to 'localhost'.
How can I do, then?
Leave localhost un-changed .
Add the hostname show in ur license file in /ect/hosts .
U can use 'hostname' in command line to modify system hostname .
I have no idea if it is related to license's 'hostname' .