a colleague got an email from letsencypt about a site they've setup standalone. which contains the following: TLS-SNI-01 validation is reaching end-of-life. It will stop working temporarily on February 13th, 2019, and permanently on March 13th, 2019. Any certificates issued before then will continue to work for 90 days after their issuance date. You need to update your ACME client to use an alternative validation method (HTTP-01, DNS-01 or TLS-ALPN-01) before this date or your certificate renewals will break and existing certificates will start to expire. more info here: https://community.letsencrypt.org/t/how-to-stop-using-tls-sni-01-with-certbot/83210 which also states: If the version is less than 0.28, you need to upgrade your Certbot. Visit https://certbot.eff.org/ 3.9k and follow the instructions for your webserver and OS, it also mentions removing references to tls-sni-01 in files in /etc/letsencrypt/renewal. having checked, there are no such references, but the certbot version from the ubuntu 18.04 repo is 0.23. is this anything we need to be worried about? or does ispconfig configure letsencrypt in a way that already avoids this issue?