Create, Prepare and Deploy a new Letsencrypt certificate for a Zimbra domain Cf. https://wiki.zimbra.com/wiki/Installing_a_LetsEncrypt_SSL_Certificate

certbot certonly --standalone --preferred-challenges http -d example.com certbot help

1. Get the certificate (git clone) and add your emails to the emails.txt file (notification)
2. In sudo, chmod +x /path/to/file/zimbra-letsencrypt.sh
3. In sudo, /path/to/file/zimbra-letsencrypt.sh

Append your crontab in sudo with the following (sudo crontab -e)
0 2 * * * root /usr/bin/certbot renew --deploy-hook "/path/to/file/zimbra-letsencrypt.sh"