If you have encountered following error,
Domain: xxx.xxx.com
Type: malformed
Detail: Failed to connect to xxx:443 for tls-sni-01
challenge: Server only speaks HTTP, not TLS
Make sure you have following lines in your Apache virtual host conf file
SSLCertificateFile /etc/ssl/certs/ssl-cert-snakeoil.pem
SSLCertificateKeyFile /etc/ssl/private/ssl-cert-snakeoil.key
Include /etc/letsencrypt/options-ssl-apache.conf