Install Zimbra Ubuntu 20.04

apt-get update
apt-get install dnsmasq
edit /etc/hosts
edit ip /etc/network/interfaces
edit /etc/dnsmasq.conf

server=8.8.8.8
listen-address=127.0.0.1
domain=example.com
mx-host=example.com,zmail.example.com,0
address=/zmail.example.com/172.16.1.100

systemctl restart dnsmasq

Test DNS
dig mx example.com

Install Zimbra