Let's Encryp Debian 8

Cert Bot install

sudo nano /etc/apt/sources.list.d/backports.list

Put this inside the file

deb http://ftp.debian.org/debian jessie-backports main

Run:

sudo apt-get install python-certbot-apache -t jessie-backports

Apache

To generate certificates & configure apache:

certbot --apache

To generate certificates only

certbot --apache certonly

Test auto renewall with (certificates are valid for 90days):

certbot renew --dry-run

Exim4

sudo certbot certonly --standalone -d mail.domain.com

Certificate files will be located as follows:

cert = /etc/letsencrypt/live/mail.domain.com/cert.pem
privkey = /etc/letsencrypt/live/mail.domain.com/privkey.pem
chain = /etc/letsencrypt/live/mail.domain.com/chain.pem
fullchain = /etc/letsencrypt/live/mail.domain.com/fullchain.pem