Linux hostname may be used in a lot of apps, mainly in email services.
We need to change
HOSTNAME value in
/etc/sysconfig/network and add new hostname to
hostnamectl set-hostname <your new hostname>
Debian 7 Wheezy
vim /etc/hostname vim /etc/hosts
All distros should be rebooted after new hostname have been changed. You can restart services but that will take probably longer.