Guide for installing zimbra on ubuntu 16.04.
If you use clouldflare or another dns service provider you can skip bind part.
install certbot on ubuntu 16.04
On Ubuntu systems, the Certbot team maintains a PPA. Once you add it to your list of repositories all you’ll need to do is apt-get the following packages.
$ sudo apt-get update
$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt-get update
$ sudo apt-get install python-certbot-apache
Reference: https://help.ubuntu.com/community/Repositories/Ubuntu#Adding_PPAs