For Apache;

sudo vim /etc/apache2/sites-enabled/000-default-le-ssl.conf
1. sudo vim /etc/letsencrypt/options-ssl-apache.conf
2. SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1
3. sudo systemctl restart apache2

For Nginx

  1. sudo vim /etc/letsencrypt/options-ssl-nginx.conf
  2. ssl_protocols TLSv1.2;
  3. sudo systemctl restart nginx

For SSL Test;

https://www.ssllabs.com/ssltest/